46. If X and Y have the joint probability distribution f(-1,0) = 0, f(-1, 1) = *, f (0, 0) = 6, f(0, 1) = 0, f (1,0) = 1, and f (1, 1) = 5, show that (a) cov(X, Y) = 0; (b) the two random variables are not independent