An interviewer is given a list of people she can interview. If the interviewer needs to interview 5 people, and if each person (independently) agrees to be interviewed with probability 2/3, what is the probability that her list of people will enable her to obtain her necessary number of interviews if the list consists of
(a) 5 people and
(b) 8 people?
For part (b), what is the probability that the interviewer will speak to exactly
(c) 6 people and
(d) 7 people on the list?