Question 57
Six distinguishable players are participating in a tennis tournament. Each player plays one match of tennis against every other player. There are no ties in this tournament—each tennis match results in a win for one player and a loss for the other. Suppose that whenever $A$ and $B$ are players in the tournament such that $A$ wins strictly more matches than $B$ over the course of the tournament, it is also true that $A$ wins the match against $B$ in the tournament. In how many ways could the tournament have gone?