Students could explore for the best cable route by inspecting the curve traced out when the purple point is dragged, i.e. generating multiple paths and their associated costs, or by looking at the cost values in the spreadsheet. Dragging the point slowly traces a more complete curve and more closely spaced values in the spreadsheet.

Try this using the applet with GeoGebra tools.

The determination of the minimum point could be improved by changing the axes scales in the Graphics window.

The GeoGebra Spreadsheet operates as a reduced version of Excel and has a Minimum tool.   Selecting the values in Column B (TotalCost) and clicking on this tool will locate the least cost.