(1) A consumer has utility function U(1L'1,1L'2) = V1151 + V1152. (a) In the same graph, draw the indifference curves {($1,302) | U(x1,x2) = 2} and identify the upper contour set {(xl,x2) | U(x1, x2) 2 2}. (b) Are his preferences monotone? (c) Are his preferences convex? Is U quasiconcave? Justify your answers formally