The probabilities that a service station will pump gas into $0,1,2,3,4,$ or 5 or more cars during a certain 30-minute period are 0.03,0.18,0.24,0.28 , $0.10,$ and $0.17,$ respectively. Find the probability that in this 30 -minute period
(a) more than 2 cars receive gas;
(b) at most 4 cars receive gas;
(c) 4 or more cars receive gas.