There is $540 available to build a rectangular pen with two fences through the inside as shown. The fence in the back costs $2 per foot, the fences...

There is $540 available to build a rectangular pen with two fences through the inside as shown. The fence in the back costs $2 per foot, the fences on the inside cost $1.50 per foot, the side fences cost $3 per foot, and the front fence, which is decorated, costs $10 per foot. What are the dimensions of the rectangular pen of greatest area that can be built with the available funds?