1. Here are some utility functions. Find a) the marginal utility with respect to 21, b) the marginal utility with respect to x2, c) the marginal rate of substitution between z, and 12. (a) u(11, 12) = 201 + 312 (b) u(21, 12) = 421 + 612 (c) u(21, 12) = am + 612 (d) u(11, 12) = 2VI1 + 12 (e) u(21, 12) = In(21) + 12 (f) u(51 , 12) = v(1 ) + 12 (g) u(21, 12) = 11 12 (h) u($1, 12) = 1712 (i) u(21, 12) = (x1 + 2)(12 + b) (j) u(21, 12) = (x1 + a)(12 +b) (k) u(21, 12) = ritz