A small house was built on an island off a perfectly straight shoreline. The point B on the shoreline that is closest to the island is exactly 5 miles from the island. Eight miles east of B is the closest source of fresh water to the island. A pipeline is to be built from the island to the source of fresh water by laying pipe underwater in a straight line from the island to a point Q on the shoreline between B and the water source, and then laying pipe on land along the shoreline from Q to the source. It costs 5000 dollars per mile to lay the pipe under the water and 3125 dollars per mile to lay pipe on land. How far east of B should Q be located in order to minimize the total construction costs?