Posted by **Z32** on Monday, November 2, 2009 at 11:36am.

A fence is to be built to enclose a rectangular area of 280 square feet. The fence along three sides is to be made of material that costs 6 dollars per foot, and the material for the fourth side costs 15 dollars per foot. Find the length L and width W (with W<= L) of the enclosure that is most economical to construct.