Minimum Cost

Author:
BHNmath

Problem

A power line needs to be run to a new cottage being built on an island that is 400 m from the shore of a lake. The main power line ends 3 km away from the point on the shore that is closest to the island. The cost of laying the power line under water is twice the cost of laying the power line on land. How should the line be placed to minimize the total cost?