need it quick

Let Yl, Yo. . .., Y, be a random sample from a Normal distribution with mean a and variance o'. On HW 7, you will look at the Cramer Rao Lower Bound for the parameter _. The Cramer-Rao Lower Bound for the parameter of is (a) Show the statistic S. is an unbiased estimator of or. (b) Find the variance of the statistic S?. (c) Explain why you cannot use the Cramer-Rao lower bound to conclude 5? is the MVUE for of. ( You will do this with sufficient statistics on HW 7)