Instead of (8.23), write X = 1 + 2 + + a, where j = 1 or 0 depending on whether or not the

Instead of (8.23), write X = η1 + η2 + ··· + ηa, where ηj = 1 or 0 depending on whether or not the jth element representing success was selected. Use this representation to derive formulas for the mean and variance of X as given in Theorem 8.2.2.