64. The number of accidents that a person has in a given year is a Poisson random variable with mean A. However, suppose that the value of A changes from person to person, being equal to 2 for 60 percent of the population and 3 for the other 40 percent. If a person is chosen at random, what is the probability that he will have

(a) 0 accidents and

(b) exactly 3 accidents in a year? What is the conditional probability that he will have 3 accidents in a given year, given that he had no accidents the preceding year?