Calculus in application

1. A rectangular field is to be fenced against the side of a barn, and then subdivided perpendicular to the barn to keep the horses and cows separate. The outer three sides are made up of a strong wood that costs $125/ft while the inside subdivision fence will cost $80/ft. If the field should have a total area of 2000ft?, determine the dimensions so that the cost of fencing is a minimum. (8 marks)