A rectangular box is to have a square base and a volume of 81 ft3. If the material for the base costs 5 cents per square foot, material for the top costs 31 cents per square foot, and the material for the sides costs 6 cents per square foot, determine the dimensions of the box (in feet) that minimize the total cost of materials used in constructing the rectangular box. Width of the base, x = feet Height of the box, y = feet