One thousand six hundred dollars are available to fence in a rectangular garden. The fencing for the north and south sides of the garden costs $20 per foot. The fencing for the east and west sides costs $25 per foot. Find the dimensions of the largest possible garden. Let x be the length of the north side of the fence and y be the length of the east side of the fence. Identify the function f(x,y) to be maximized and the constraint function g(x,y). f(x,y) = and g(x,y) =