In horse racing, a trifecta bet is one where you need to pick the first three finishers of the race in the exact order in order to win the bet and a boxed trifecta bet is one where you need to pick the first three finishers in the race in any order to win. In the 1945 Kentucky Derby a total of 13 horses raced and if a person decided to make a bet in the race:
a) How many different possible trifecta bets could they have made?
b) How many different possible boxed trifeca bets could they have made?