5. if the utility function oi an individual takes the form U = U(31,12)=(Xt+2}2(12 + 333 where U is total utility, and x] and x2 are the quantities of two commodities consumed: (0) Find the marginal-utility function of each of the two commodities. (b) Find the value of the marginal utility of the first commodity when 3 units of each commodity are consumed.