Open-box Problem. An open-box (top open) is made from a rectangular material of dimensions a = 15 inches by b = 11 inches by cutting a square of side ax at each corner and turning up the sides (see the figure). Determine the value of a that results in a box the maximum volume. Following the steps to solve the problem. Check Show Answer only after you have tried hard. (1) Express the volume V as a function of x: V = (15 - 2x) (11 - 2x)x (2) Determine the domain of the function V of x (in interval form): (3) Expand the function V for easier differentiation: V = (4) Find the derivative of the function V: V'= (5) Find the critical point(s) in the domain of V