6. The joint probability density function of X and Y is given by p(x,y) = 2(x +y) [0

6. The joint probability density fimction of X and Y is given by (a) Find cov(X, Y) (b) Let I'V X + Y. Find the distribution fiunction of W. (c) Define Z p(X)E(YlX). Find E(Z) and var(Z). (The calculation might be complicated) (d) Let 0 var (W) and (Xi, be random sample, from p (x, y) . What is the sample analogue estimator? Is it consistent for 0?