A cable is to be run from a power plant on one side of a

river to a factory on the other side. It costs $4 per

meter to run the cable over land, while it costs $5 per

meter to run the cable under water. Suppose the river

is 300 meters wide and the factory is 1000 meters

downstream from the power plant.

What is the most economical route to lay the cable?

How much will it cost?