8. A tetrahedron shaped die gives one of the numbers 1, 2, 3, 4 with equal probabilities. We roll
two of these dice and denote the two outcomes by X1 and X2. Let Y1 =(minpX1, X2) and
Y2 = |X1 - X2|.
(a) Find the joint probability mass function of X1 and X2.
(b) Find the joint probability mass function of Y1 and Y2.
(c) Compute E[Y1Y2]