(a) Given the joint characteristic function of a pair of random variables, X, Y (1, 2)....

(a) Given the joint characteristic function of a pair of random variables, Φ X, Y (ω1, ω2). How do we get a marginal characteristic function of one of the random variables, say, Φ X (ω) from the joint characteristic function?
(b) Repeat part (a) for the joint PGF, H X, Y (z1, z2.