Question 4: Let X and Y be random variables. The joint probability density function of X: is as follows: fxy(x,y) = {xy, 0≤x≤ 1:0≤ y ≤ 1elsewhere a) Find the value of k that makes f xY (x,y) a joint probability density function.b) Find the marginal density functions for the random variable X and for the random variable Y.c) Find P(X > 1/2; Y < 3/4)d) Find mu_{X} = E(X) mu_{Y} = E(Y) and COV (X,Y)