A three-dimensional box without a lid is to be made of a material that costs $1 per square foot for the sides and $3 per square foot for the bottom. The box is to contain 27 cubic feet. Let I, w, and h denote, respectively, the length, width, and height of the box. Since the box must contain 27 cubic feet, we must have I wh = 27, or, equivalently, h = 27 / (Iw). Use this expression for h to find a formula for the cost of a box having length I and width w.