The utility of a consumer consuming two goods, the quantities of which are x; and x2, is given by U(x1,x2) = 7 + 24x1 3.15% + 8x2 2x3 Select one: a. The utility function has a local maximum at its stationary point. b. The utility function has at least one stationary point. c. The utility function is strictly concave. d. The utility function has a global maximum at its stationary point. e. The utility function has a local minimum at its stationary point