please help with practice problem

8. Let X1, X2 be a random sample of size n = 2 from a population having gamma distribution with probability density function 1 f(xla, 0) = r(a) Aa e ex -1, x > 0, where a > 0 and 0 > 0 are unknown parameters, and I(a) is the usual gamma function. (a) Show that T = (X1 + X2, X1X2) is a minimal sufficient statistic; (b) Are T1 = (1 In(X1X2|, X1 + X2) and T2 = (In X, + In X2, In(X1 + X2)) sufficient statistics; here, for any real number x, |x| denotes the modulus of x; (c) Find the minimum variance unbiased estimator of V(X1)