I need to count how many different ways there are to arrange the four teams in a sequence, given the constraints of the tournament. I notice that the first and second place teams must have won their Saturday games, and the third and fourth place teams must have lost their Saturday games. So the sequence of the first and second place teams is determined by the outcome of the Saturday games, and the same for the third and fourth place teams. Therefore, I can think of the ranking sequence as two pairs of teams, where each pair can be arranged in two ways. For example, if A and C win on Saturday, then the first and second place teams are either AC or CA, and the third and fourth place teams are either BD or DB. So for each possible outcome of the Saturday games, there are 2 x 2 = 4 possible ranking sequences. But how many possible outcomes are there for the Saturday games? Well, each game has two possible outcomes, and there are two games, so there are 2 x 2 = 4 possible outcomes for the Saturday games. So the total number of possible four-team ranking sequences is the product of the number of possible outcomes for the Saturday games and the number of possible ranking sequences for each outcome, which is 4 x 4 = 16. 
On the Saturday of a weekend softball tournament, Team A plays Team B and Team C plays Team D. Then on Sunday, the two Saturday winners play for first and second places while the two Saturday losers play for third and fourth places. There are no ties. One possible ranking of the team from first place to fourth place at the end of the tournament is the sequence ACBD. What is the total number of possible four-team ranking sequences at the end of the tournament?