For each of the following distributions, give the Method of Moments Estimator in terms of the sample averages Xn and Xn^2, assuming we have access to n i.i.d observations X1,..., Xn. In other words, express the parameters as functions of E[X1] and E[X1^2] and then apply these functions to Xn and Xn^2

a) Xi ~ Ber(p), pe(0,1)

b) Xi ~ Poiss (lambda)

c) Xi ~ Exp(lambda)

d) Xi ~ N(mu, sigma^2) (i.e. find Method of Moments Estimator for mu and sigma^2)