14. Let X and Y be two discrete random variables with the identical set of possible values A = {a1, a2, . . . , an}, where a1, a2, . . . , an are n different real numbers. Show that if E(Xr ) = E(Y r ), r = 1, 2,...,n − 1, then X and Y are identically distributed. That is, P (X = t) = P (Y = t) for t = a1, a2, . . . , an.