The joint pmf of a bivariate r.v.(X,Y) is given by
Pxy (xi,yj) = k(2xi + yj) xi= 1,2 ; yj =1,2
0 otherwise
a-Find the mean and the variance of X.
b-Find the mean and the variance of Y.
c-Find the covariance of X and Y.
d-Find the correlation coefficient of X and Y.