X1,…,Xn is an iid sequence of exponential random variables, each with expected value 5 . (a) What is Var[M_9(X)], the variance of the sample mean based on nine trials? (b) What is P[X1>7], the probability that one outcome exceeds 7 ? (c) Use the central limit theorem to estimate P[M_9​ (X)>7], the probability that the sample mean of nine trials exceeds 7 .