can you solve problem c?

3.7.59 It can take up to four days after you call for service to get your computer repaired. The computer company charges for repairs according to how long you have to wait. The number of days D until the service technician arrives and the service charge C', in dollars, are described by 1 2 3 4 0.2 04 O03 OQ.1 and 90 for 1-day service, 70 for 2-day service, 4Q for 3-day service, 4Q for 4-day service. (a) What is the expected waiting time [tp = E|D]? (b) What is the expected deviation E|D pep]? (c) Express C' as a function of D. (d) What is the expected value E[C]