Consider the unit disc D = {(x, y) | x^2 + y^2 <= 1}. Suppose that we choose a point (X,Y) uniformly at random in D. That is, the joint PDF of X and Y is given by: f_XY(x,y) = 1/pi if (x,y) in D, 0 otherwise. Find the following (12 marks): (a) The marginal PDFs of X and Y. (b) The pdf f_Z(z) such that Z = min(X,Y). (c) Cov(XY,X+Y).