X1 Q2. Suppose that the discrete random vector has the Multinomial distribution with the joint probability mass function tabulated below. X 2 X1 0 1 2 3 0 0. 125 0. 225 0. 135 0. 027 1 0. 15 ). 18 0. 054 X2 No 0.06 0. 036 3 0. 008 Enter all numbers as decimal numbers (4 decimal places are sufficient). (a) Identify the marginal distribution of X1 (2 marks) X]~Bi(3, (b) Identify the marginal distribution of X2 (1 mark) X2~Bi(3. (c) Hence identify the joint distribution (3 marks; 1 mark for each parameter) X1 ~ Mu X 2 (d) Identify the marginal distribution of X1 + X2 (1 mark) Xi + X2~ Bi(3 (e) Find the covariance (1 mark) cov(X1 X2) =