A large stockpile of used pumps contains 10% that are in need of repair. A female maintenance worker is sent to the stockpile with four repair kits. She selects pumps at random and tests them one at a time. If the pump works, she sets it aside for future use. However, if the pump does not work, she uses one of her repair kits on it. Suppose that it takes 5 minutes to test a pump that is in working condition and 20 minutes to test and repair a pump that does not work.

(a.2) Find the mean and variance of the total time it takes the maintenance worker to use her first repair kits.