A nationwide survey of college seniors by a university revealed that almost 80​% disapprove daily pot​ smoking, according to a report in a magazine. If 11 seniors are selected at random and asked their​ opinion, find the probability that the number who disapprove of smoking pot daily is​ (a) anywhere from 7 to 10​, ​(b) at most 5 and​ (c) not less than 8.