please help

Let X" be a random variable with the following probability distribution. Value x of X P(X=x) -10 0.25 0 0.10 10 0.20 20 0.15 30 0.20 40 0.10 Complete the following. (If necessary, consult a list of formulas.) (a) Find the expectation E (X) of 1. X 5 ? E(X) = 1 (b) Find the variance var(X") of X. var (X) = 1