9. Suppose that X1, X2, X3, .. . "IP N(u, 62) for some u and some o2 > 0, and let Yn = X1 - Xn for each n. (a) What is Cov (Xn, Yn)? (b) Are Xn and Yn necessarily independent? Explain. 10. Suppose that X1, X2, X3, ... ~Exp()) for some > > 0. For sufficiently large n, is Xn approximately standard normal in its distribution? Explain