This one requires some drawing...I think. A diagram maybe? ^^"

Town A is 11 miles from a straight river and town B is 6 miles from the same river. The distance from town A to town B is 13 miles. A pumping station is to be built along the river to supply water to both towns. Where should the pumping station be built so that the sum of the distances from the pumping station to the town is a minimum?

Thanks for the help. =)