Suppose two random variables X and Y have a joint probability density function f(xy) = 2e^(-4y) for 0 < x < y. f(x,y) = 0 otherwise. Let Z = max{X, Y}. (a) Find the marginal probability density functions of X and Y, respectively. Are X and Y independent? (b) Find the probability density function of Z. (c) Find the expectation E(Z).