There are 20 students on the swim team.
a) If the coach needs to pick 4 of them for a relay, how many ways can they pick them?
b) If the coach needs to pick 10 of them for a tournament, how many ways can they pick them?
c) If 10 swimmers go to a competition, how many ways can 1st, 2nd, and 3rd place occur for this
competition?
d) If all 20 swimmers go to a competition, how many ways can 1st, 2nd, and 3rd place occua fas
this competition?