Question

According to a study published by a group of University
of Massachusetts sociologists, approximately
60% of the Valium users in the state of Massachusetts
first took Valium for psychological problems. Find the
probability that among the next 8 users from this state
who are interviewed,
(a) exactly 3 began taking Valium for psychological
problems;
(b) at least 5 began taking Valium for problems that
were not psychological