For each of the following utility functions, find the MRS1,2 = MU, MU1 at the bundle (19, 3). a) u(x1, X2) = Inx1 + Inx2 b) u(x1, x2) = min{ x1, x2} c) u(x1, X2) = 4x1 +9x2 d) u(x1, X2) = Inx1 + 2x2 e) u(x1, X2) = (4x1 + 9x2)3 f) u(x1, x2) = x1+ x3