Suppose X and Y are random variables with the given joint density function J0 1e 0 5x 0 2y if x 0 y 20 0 1e otherwise f x y a Is f a joint density function Yes No b Find P Y 3 Round your answer to four decimal places 0 5488 Find P X 3 Y 6 Round your answer to four decimal places 0 4287 X c Find the expected value of X Find the expected value of Y