X1,..., Xn is an iid sequence of exponential random variables, each with expected value 5.
(a) What is Var[M9(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) Estimate P[M9(X) > 7], the probability that the sample mean of nine trials exceeds 7?