3. (10 scores) Assume that random variables X and Y have the following joint probability density function as f(x,y) = {0} (1, Osx < 1, lyl sx otherwise (1) Find the marginal probability density functions fx(x) and fr(y) of X and Y, respectively. (2) Calculate E(X) and E(Y) (3) Calculate the covariance Cov(X,Y).