# Question: Prove Proposition 2 1 when a X and Y have a joint

Prove Proposition 2.1 when

(a) X and Y have a joint probability mass function;

(b) X and Y have a joint probability density function and g(x, y) ≥ 0 for all x, y.

(a) X and Y have a joint probability mass function;

(b) X and Y have a joint probability density function and g(x, y) ≥ 0 for all x, y.

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