In a newspaper ad, a car deal lists 3 cars. If the numbers of inquiries he will get about these cars may be regarded as independent random variables having Poisson distributions with the parameters lambda sub 1= 3.6, lambda sub 2 = 5.8, and lambda sub 3 = 4.6. What are the probabilities that altogether he will recieve:
a) fewer than 10 inquires about these cars;
b) anywhere from 15 to 20 inquires;
c) at least 18?