A box contains 12 ribbons of which 4 are blue and 3 are green. Suppose U and Vare the number of and green ribbons selected from the box and P(U = u; V = v) = p(u, v) is the joint probability of the hivariate random variable (U, V) () p(u, v) ) P(U <= 2, V >= 2) ) P(U - V < 2) ( d) the marginal distributions of U and