(20) Graduate student only. Let V and W be discrete random variables defined on some probability space with a joint pmf Puw(vw) a. Prove that E[v+w] = E[v] +E[w]. Do not assume independence. b. Prove that if V and Ware independence, then E[V*W] =E[v]*E[w] Assume that V and W are independence and variance of and show that the variance of V+W is of+w = 0 + ou | C