A high school club consisting of 23 students has 8 junior members and 15 senior members. Two of the members are the club president and vice president. They want to form a school dance committee consisting of five members. Assuming that each committee is equally likely, what is the probability that (a) The committee formed does not contain either the president nor the vice president. (b) There is at least one junior on the committee. (c) Two juniors and three seniors are on the committee.