When an opinion poll calls landline telephone numbers at random, approximately 30% of the numbers are working residential phone numbers. The remainder is either non-residential, non- working, or computer/fax numbers. You watch the random dialing machine make 20 calls. Suppose X= working residential numbers a. What is the probability that exactly three calls reach working residential numbers? b. What is the probability that at most three calls reach working residential numbers? c. What is the probability that at least three calls reach working residential numbers? d. What is the probability that fewer than three calls reach working residential numbers? e. What is the probability that more than three calls reach working residential numbers?