The owner of a lumber store wants to construct a fence to enclose
a rectangular outdoor storage area adjacent to the store, using part of
the side of
the store (which is 240 feet long) for part of one of the sides.
(See the figure below.) There are 420 feet of
fencing available to complete the job. Find the length
of the sides parallel to the store and perpendicular that will
maximize the total area of the outdoor enclosure.

Note: you can click on the image to get a enlarged view.