Consider the random variables X and Y with joint density function f(x, y) = {c(x + y), 0 <= x, y <= 1, 0, elsewhere. (a) Find c. (b) Find the marginal distribution of X. (c) Find P(X > 0.5, Y > 0.5) and P(X > Y). (d) Find the mean and variance of X and X + Y. (e) Are X and Y independent? Find Cov(X, Y). (f) Find the mean and variance of XY.