A fish tank is a rectangular prism whose height is 4 inches more than its width and whose length is three times as long as the width. Find the volume of the tank as a function of height.

V =lwh = hwl = h(h-4){3(h-4)} = 3h(h-4)^2 = 3h(h^2 - 8h + 16) = 3h^3 - 24h^2 +48h