Basic Rules of Expectation, Variance, and Covariance Problem 1. Consider random variables X, Y, Z with X = 2Y + 5Z and E(Y) = 10, E(Z) = 4, Var(Y) = 25, Var(Z) = 10, Cov(Y, Z) = 0.65. Find the values of a) E(3X). b) Var (2X). c) What are the answers to a) and b) if X = 3 + 2Y + 5Z