diff --git a/cad/images.drawio b/cad/images.drawio
index 43efeff..4ab4352 100644
--- a/cad/images.drawio
+++ b/cad/images.drawio
@@ -1,31 +1,221 @@
-<mxfile host="Electron" modified="2023-07-02T08:47:53.457Z" agent="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) draw.io/21.3.7 Chrome/112.0.5615.204 Electron/24.5.0 Safari/537.36" etag="9V9i2ZHjO2KAMOXz_0WO" version="21.3.7" type="device">
-  <diagram name="Page-1" id="apkLY82v2svt43NLXheB">
-    <mxGraphModel dx="144" dy="113" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="850" pageHeight="1100" math="0" shadow="0">
+<mxfile host="Electron" modified="2023-07-23T19:25:40.038Z" agent="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) draw.io/21.3.7 Chrome/112.0.5615.204 Electron/24.5.0 Safari/537.36" etag="xQALbCd7-RyYv2gA3HXK" version="21.3.7" type="device" pages="3">
+  <diagram id="3sszMtRI6r7jZAS6h2Vp" name="a solution">
+    <mxGraphModel dx="1147" dy="671" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="1169" pageHeight="827" math="0" shadow="0">
       <root>
         <mxCell id="0" />
         <mxCell id="1" parent="0" />
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-12" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;" edge="1" parent="1" source="rbrn1IwdH5oRhUIE0Q6u-1" target="rbrn1IwdH5oRhUIE0Q6u-3">
+        <mxCell id="VBj0H-3z08zBr2uviqVi-1" value="Laser head" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#f5f5f5;fontColor=#333333;strokeColor=#666666;" vertex="1" parent="1">
+          <mxGeometry x="280" y="80" width="120" height="120" as="geometry" />
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-2" value="Laser&lt;br&gt;stand" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#f5f5f5;fontColor=#333333;strokeColor=#666666;" vertex="1" parent="1">
+          <mxGeometry x="80" y="80" width="80" height="340" as="geometry" />
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-3" value="Laser arm" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#f5f5f5;fontColor=#333333;strokeColor=#666666;" vertex="1" parent="1">
+          <mxGeometry x="40" y="100" width="240" height="80" as="geometry" />
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-4" value="Bed" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#f5f5f5;fontColor=#333333;strokeColor=#666666;" vertex="1" parent="1">
+          <mxGeometry x="40" y="420" width="400" height="20" as="geometry" />
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-5" value="" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#e1d5e7;strokeColor=#9673a6;" vertex="1" parent="1">
+          <mxGeometry x="110" y="40" width="20" height="40" as="geometry" />
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-6" value="Set screw" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#e1d5e7;strokeColor=#9673a6;" vertex="1" parent="1">
+          <mxGeometry x="80" y="50" width="80" height="20" as="geometry" />
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-7" value="Lens" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#dae8fc;strokeColor=#6c8ebf;" vertex="1" parent="1">
+          <mxGeometry x="300" y="200" width="80" height="20" as="geometry" />
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-16" value="" style="endArrow=none;dashed=1;html=1;dashPattern=1 3;strokeWidth=2;rounded=0;" edge="1" parent="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="380" y="220" as="sourcePoint" />
+            <mxPoint x="440" y="220" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-17" value="" style="endArrow=classic;startArrow=classic;html=1;rounded=0;" edge="1" parent="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="420" y="400" as="sourcePoint" />
+            <mxPoint x="420" y="220" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-18" value="calibrated&lt;br&gt;height" style="edgeLabel;html=1;align=center;verticalAlign=middle;resizable=0;points=[];" vertex="1" connectable="0" parent="VBj0H-3z08zBr2uviqVi-17">
+          <mxGeometry x="-0.139" y="1" relative="1" as="geometry">
+            <mxPoint y="-10" as="offset" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-19" value="" style="endArrow=none;html=1;rounded=0;exitX=0.515;exitY=0.002;exitDx=0;exitDy=0;exitPerimeter=0;" edge="1" parent="1" source="VBj0H-3z08zBr2uviqVi-20">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="330" y="350" as="sourcePoint" />
+            <mxPoint x="350" y="240" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-20" value="Object" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#ffe6cc;strokeColor=#d79b00;" vertex="1" parent="1">
+          <mxGeometry x="280" y="400" width="120" height="20" as="geometry" />
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-21" value="" style="endArrow=none;html=1;rounded=0;exitX=0.483;exitY=-0.003;exitDx=0;exitDy=0;exitPerimeter=0;" edge="1" parent="1" source="VBj0H-3z08zBr2uviqVi-20">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="330" y="400" as="sourcePoint" />
+            <mxPoint x="330" y="240" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-22" value="" style="endArrow=none;html=1;rounded=0;" edge="1" parent="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="350" y="240" as="sourcePoint" />
+            <mxPoint x="390" y="230" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-23" value="" style="endArrow=none;html=1;rounded=0;" edge="1" parent="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="330" y="240" as="sourcePoint" />
+            <mxPoint x="290" y="230" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-24" value="" style="endArrow=none;html=1;rounded=0;" edge="1" parent="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="290" y="230" as="sourcePoint" />
+            <mxPoint x="290" y="220" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-25" value="" style="endArrow=none;html=1;rounded=0;" edge="1" parent="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="390" y="230" as="sourcePoint" />
+            <mxPoint x="390" y="220" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-26" value="" style="endArrow=none;html=1;rounded=0;" edge="1" parent="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="290" y="220" as="sourcePoint" />
+            <mxPoint x="390" y="220" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-27" value="Stick" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1">
+          <mxGeometry x="310" y="220" width="60" height="20" as="geometry" />
+        </mxCell>
+        <mxCell id="VBj0H-3z08zBr2uviqVi-30" value="" style="endArrow=none;dashed=1;html=1;dashPattern=1 3;strokeWidth=2;rounded=0;" edge="1" parent="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="400" y="400" as="sourcePoint" />
+            <mxPoint x="440" y="400" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+      </root>
+    </mxGraphModel>
+  </diagram>
+  <diagram id="MNFISAVLOub1gNjFvxmU" name="installation">
+    <mxGraphModel dx="1434" dy="839" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="1169" pageHeight="827" math="0" shadow="0">
+      <root>
+        <mxCell id="0" />
+        <mxCell id="1" parent="0" />
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-1" value="Laser head" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#f5f5f5;fontColor=#333333;strokeColor=#666666;" parent="1" vertex="1">
+          <mxGeometry x="280" y="80" width="120" height="120" as="geometry" />
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-4" value="Laser&lt;br&gt;stand" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#f5f5f5;fontColor=#333333;strokeColor=#666666;" parent="1" vertex="1">
+          <mxGeometry x="80" y="80" width="80" height="340" as="geometry" />
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-2" value="Laser arm" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#f5f5f5;fontColor=#333333;strokeColor=#666666;" parent="1" vertex="1">
+          <mxGeometry x="40" y="100" width="240" height="80" as="geometry" />
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-3" value="Bed" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#f5f5f5;fontColor=#333333;strokeColor=#666666;" parent="1" vertex="1">
+          <mxGeometry x="40" y="420" width="400" height="20" as="geometry" />
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-5" value="" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#e1d5e7;strokeColor=#9673a6;" parent="1" vertex="1">
+          <mxGeometry x="110" y="40" width="20" height="40" as="geometry" />
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-6" value="Set screw" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#e1d5e7;strokeColor=#9673a6;" parent="1" vertex="1">
+          <mxGeometry x="80" y="50" width="80" height="20" as="geometry" />
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-7" value="Lens" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#dae8fc;strokeColor=#6c8ebf;" parent="1" vertex="1">
+          <mxGeometry x="300" y="200" width="80" height="20" as="geometry" />
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-20" value="" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#d5e8d4;strokeColor=#82b366;" parent="1" vertex="1">
+          <mxGeometry x="220" y="120" width="40" height="50" as="geometry" />
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-21" value="Sensor" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#d5e8d4;strokeColor=#82b366;" parent="1" vertex="1">
+          <mxGeometry x="220" y="150" width="40" height="20" as="geometry" />
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-22" value="" style="endArrow=classic;html=1;rounded=0;exitX=0.25;exitY=1;exitDx=0;exitDy=0;entryX=0.5;entryY=0;entryDx=0;entryDy=0;strokeColor=#ff0000;" parent="1" source="NZMJPotCeYKzqYKeXrxm-21" target="NZMJPotCeYKzqYKeXrxm-3" edge="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="230" y="270" as="sourcePoint" />
+            <mxPoint x="280" y="220" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-23" value="" style="endArrow=classic;html=1;rounded=0;exitX=0.5;exitY=0;exitDx=0;exitDy=0;entryX=0.75;entryY=1;entryDx=0;entryDy=0;strokeColor=#ff0000;" parent="1" source="NZMJPotCeYKzqYKeXrxm-3" target="NZMJPotCeYKzqYKeXrxm-21" edge="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="270" y="380" as="sourcePoint" />
+            <mxPoint x="320" y="330" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-24" value="Display" style="rounded=0;whiteSpace=wrap;html=1;fillColor=#d5e8d4;strokeColor=#82b366;" parent="1" vertex="1">
+          <mxGeometry x="180" y="70" width="80" height="30" as="geometry" />
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-25" value="" style="endArrow=none;html=1;rounded=0;entryX=1;entryY=0.75;entryDx=0;entryDy=0;edgeStyle=orthogonalEdgeStyle;curved=1;" parent="1" target="NZMJPotCeYKzqYKeXrxm-24" edge="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="230" y="150" as="sourcePoint" />
+            <mxPoint x="280" y="100" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-26" value="" style="endArrow=none;html=1;rounded=0;entryX=1;entryY=0.5;entryDx=0;entryDy=0;edgeStyle=orthogonalEdgeStyle;curved=1;" parent="1" target="NZMJPotCeYKzqYKeXrxm-24" edge="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="240" y="150" as="sourcePoint" />
+            <mxPoint x="270" y="103" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-27" value="" style="endArrow=none;html=1;rounded=0;entryX=1.03;entryY=0.236;entryDx=0;entryDy=0;edgeStyle=orthogonalEdgeStyle;curved=1;exitX=0.75;exitY=0;exitDx=0;exitDy=0;entryPerimeter=0;" parent="1" source="NZMJPotCeYKzqYKeXrxm-21" target="NZMJPotCeYKzqYKeXrxm-24" edge="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="250" y="160" as="sourcePoint" />
+            <mxPoint x="270" y="95" as="targetPoint" />
+            <Array as="points">
+              <mxPoint x="250" y="125" />
+              <mxPoint x="270" y="125" />
+              <mxPoint x="270" y="77" />
+            </Array>
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="NZMJPotCeYKzqYKeXrxm-28" value="" style="endArrow=none;dashed=1;html=1;dashPattern=1 3;strokeWidth=2;rounded=0;" parent="1" edge="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="380" y="220" as="sourcePoint" />
+            <mxPoint x="440" y="220" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="B5FThEVqZEJE81hVcRRr-1" value="" style="endArrow=classic;startArrow=classic;html=1;rounded=0;" parent="1" edge="1">
+          <mxGeometry width="50" height="50" relative="1" as="geometry">
+            <mxPoint x="420" y="420" as="sourcePoint" />
+            <mxPoint x="420" y="220" as="targetPoint" />
+          </mxGeometry>
+        </mxCell>
+        <mxCell id="B5FThEVqZEJE81hVcRRr-2" value="calibrated&lt;br&gt;height" style="edgeLabel;html=1;align=center;verticalAlign=middle;resizable=0;points=[];" parent="B5FThEVqZEJE81hVcRRr-1" vertex="1" connectable="0">
+          <mxGeometry x="-0.139" y="1" relative="1" as="geometry">
+            <mxPoint y="-10" as="offset" />
+          </mxGeometry>
+        </mxCell>
+      </root>
+    </mxGraphModel>
+  </diagram>
+  <diagram name="controlloop" id="apkLY82v2svt43NLXheB">
+    <mxGraphModel dx="1434" dy="839" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="1169" pageHeight="827" math="0" shadow="0">
+      <root>
+        <mxCell id="0" />
+        <mxCell id="1" parent="0" />
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-12" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;" parent="1" source="rbrn1IwdH5oRhUIE0Q6u-1" target="rbrn1IwdH5oRhUIE0Q6u-3" edge="1">
           <mxGeometry relative="1" as="geometry" />
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-1" value="display" style="rounded=0;whiteSpace=wrap;html=1;" vertex="1" parent="1">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-1" value="display" style="rounded=0;whiteSpace=wrap;html=1;" parent="1" vertex="1">
           <mxGeometry x="280" y="80" width="120" height="40" as="geometry" />
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-2" value="sensor" style="rounded=0;whiteSpace=wrap;html=1;" vertex="1" parent="1">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-2" value="sensor" style="rounded=0;whiteSpace=wrap;html=1;" parent="1" vertex="1">
           <mxGeometry x="280" y="160" width="120" height="40" as="geometry" />
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-3" value="human&lt;br&gt;turning cranck" style="rounded=0;whiteSpace=wrap;html=1;" vertex="1" parent="1">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-3" value="human&lt;br&gt;changing heignt&lt;br&gt;of laser arm" style="rounded=0;whiteSpace=wrap;html=1;" parent="1" vertex="1">
           <mxGeometry x="440" y="80" width="120" height="40" as="geometry" />
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-10" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;" edge="1" parent="1" source="rbrn1IwdH5oRhUIE0Q6u-4" target="rbrn1IwdH5oRhUIE0Q6u-5">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-10" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;" parent="1" source="rbrn1IwdH5oRhUIE0Q6u-4" target="rbrn1IwdH5oRhUIE0Q6u-5" edge="1">
           <mxGeometry relative="1" as="geometry" />
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-4" value="setpoint" style="rounded=0;whiteSpace=wrap;html=1;" vertex="1" parent="1">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-4" value="setpoint" style="rounded=0;whiteSpace=wrap;html=1;" parent="1" vertex="1">
           <mxGeometry x="40" y="80" width="120" height="40" as="geometry" />
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-11" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;" edge="1" parent="1" source="rbrn1IwdH5oRhUIE0Q6u-5" target="rbrn1IwdH5oRhUIE0Q6u-1">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-11" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;" parent="1" source="rbrn1IwdH5oRhUIE0Q6u-5" target="rbrn1IwdH5oRhUIE0Q6u-1" edge="1">
           <mxGeometry relative="1" as="geometry" />
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-13" value="" style="endArrow=classic;html=1;rounded=0;exitX=0.5;exitY=1;exitDx=0;exitDy=0;entryX=1;entryY=0.5;entryDx=0;entryDy=0;" edge="1" parent="1" source="rbrn1IwdH5oRhUIE0Q6u-3" target="rbrn1IwdH5oRhUIE0Q6u-2">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-13" value="" style="endArrow=classic;html=1;rounded=0;exitX=0.5;exitY=1;exitDx=0;exitDy=0;entryX=1;entryY=0.5;entryDx=0;entryDy=0;" parent="1" source="rbrn1IwdH5oRhUIE0Q6u-3" target="rbrn1IwdH5oRhUIE0Q6u-2" edge="1">
           <mxGeometry width="50" height="50" relative="1" as="geometry">
             <mxPoint x="480" y="200" as="sourcePoint" />
             <mxPoint x="530" y="150" as="targetPoint" />
@@ -34,7 +224,7 @@
             </Array>
           </mxGeometry>
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-14" value="" style="endArrow=classic;html=1;rounded=0;entryX=0.5;entryY=1;entryDx=0;entryDy=0;exitX=0;exitY=0.5;exitDx=0;exitDy=0;" edge="1" parent="1" source="rbrn1IwdH5oRhUIE0Q6u-2" target="rbrn1IwdH5oRhUIE0Q6u-5">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-14" value="" style="endArrow=classic;html=1;rounded=0;entryX=0.5;entryY=1;entryDx=0;entryDy=0;exitX=0;exitY=0.5;exitDx=0;exitDy=0;" parent="1" source="rbrn1IwdH5oRhUIE0Q6u-2" target="rbrn1IwdH5oRhUIE0Q6u-5" edge="1">
           <mxGeometry width="50" height="50" relative="1" as="geometry">
             <mxPoint x="140" y="200" as="sourcePoint" />
             <mxPoint x="190" y="150" as="targetPoint" />
@@ -43,25 +233,25 @@
             </Array>
           </mxGeometry>
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-5" value="" style="ellipse;whiteSpace=wrap;html=1;aspect=fixed;" vertex="1" parent="1">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-5" value="" style="ellipse;whiteSpace=wrap;html=1;aspect=fixed;" parent="1" vertex="1">
           <mxGeometry x="200" y="80" width="40" height="40" as="geometry" />
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-7" value="" style="endArrow=none;html=1;rounded=0;" edge="1" parent="1">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-7" value="" style="endArrow=none;html=1;rounded=0;" parent="1" edge="1">
           <mxGeometry width="50" height="50" relative="1" as="geometry">
             <mxPoint x="210" y="100" as="sourcePoint" />
             <mxPoint x="230" y="100" as="targetPoint" />
           </mxGeometry>
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-8" value="" style="endArrow=none;html=1;rounded=0;" edge="1" parent="1">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-8" value="" style="endArrow=none;html=1;rounded=0;" parent="1" edge="1">
           <mxGeometry width="50" height="50" relative="1" as="geometry">
             <mxPoint x="220" y="110" as="sourcePoint" />
             <mxPoint x="220" y="90" as="targetPoint" />
           </mxGeometry>
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-15" value="+" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-15" value="+" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" parent="1" vertex="1">
           <mxGeometry x="180" y="80" width="20" height="20" as="geometry" />
         </mxCell>
-        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-16" value="-" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1">
+        <mxCell id="rbrn1IwdH5oRhUIE0Q6u-16" value="-" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" parent="1" vertex="1">
           <mxGeometry x="200" y="120" width="20" height="20" as="geometry" />
         </mxCell>
       </root>
diff --git a/img/a_solution.jpg b/img/a_solution.jpg
index 9880579..630e857 100644
Binary files a/img/a_solution.jpg and b/img/a_solution.jpg differ