Please solve this problem .

B5. Suppose X1 and X2 are independent Exp(1/)\\) random variables. Let 6; = a(X1 + X2) and 92 = bx/X 1X2 denote possible estimators of A, where a and b are constants. (i) Show that a = 1/2 if d; is to be an unbiased estimator of A; [4 marks] (ii) Show that b = 4/ 7r if d; is to be an unbiased estimator of A