2. (15 pts) Consider a two-commodity, X and Y, universe. Are preferences represented by the following utility functions monotonic? Explain (prove) only if your answer is NO. (a) U(x, y) = (x + 4)(y + 2) (b) U (x, y) = min{2x - 3, 2y - T} (c) U(2,y) = (x - 2)(y-2)