Fix incorrect calculation

Helios/Source/SolarPanel.cs

@@ -47,7 +47,7 @@ namespace Helios.Source
         {
             double costPerWatt;
 
-            costPerWatt = this.InstallationCost * this.PowerOutput;
+            costPerWatt = this.InstallationCost / this.PowerOutput;
 
             this.CostPerWatt = costPerWatt;