A small resort is situated on an island that lies exactly 3 miles from P, the nearest point to the island along a perfectly straight shoreline. 10 miles down the shoreline from P is the closest source of fresh water. If it costs k dollars per mile to lay pipe in land and it costs 2 k dollars per mile to lay pipe in the water, how far down the shoreline from P should the pipe from the island reach land in order to minimize the total construction costs?