Can anyone help me solve this problem with the steps please?

Problem 2. (30pts) An certain brand of upright freezer is available in three different rated capacities: 16ft3, 18ft3, and 20ft3. Let X = the rated capacity of a freezer of this brand sold at a certain store. Suppose that X has the following probability density function: X 16 18 20 P(x) 0.5 0.1 0.4 a) (10pts) Compute E(X) and E(X?) b) (10pts) If the price of a freezer having capacity X is 68X - 650, what is the expected price paid by a customer to buy a freezer. c) (10pts) What is the variance of the price paid by a customer