=+15.21. This exercise is related to Example 15.10.

(i) Verify expression (15.42).

(ii) Derive an expression for f(v, z2, z3|u) by integrating out α and β over

[0, 1] × [0, 1] from (15.42).

(iii) Verify (15.43); then derive f(z3|z2, Y ).

(iv) Similarly, derive f(z2|z3, Y)