5. Suppose that N, X1, X2, ... are independent r.v.'s with N equally likely to be 1 or 2, and X, ~ Exp(1/a). Let S = X1 . .. XN. (a) Find E(S). (b) Find Var(S).5. Suppose that N, X1, X2, ... are independent r.v.'s with N equally likely to be 1 or 2, and X, ~ Exp(1/a). Let S = X1 . .. XN. (a) Find E(S). (b) Find Var(S)