Please help answer this:

Find all the pure-strategy Nash equilibria of this game. What's the number of purestrategy Nash equilibria in the game? And explain the steps to do so.

Four players contemplate a heist. It's risky for them to communicate, and each player has to decide independently whether to participate in the heist (strategy P) or not (strategy N). Due to the elaborate security system, players need to work in pairs to succeed: the heist is successful only if exactly two or all four players participate. If the heist is successful, each of the four players gets a benefit of 2 (even those who don't participate in the heist). Every player who participates in the heist bears a cost of 1 (regardless of whether the heist succeeds or fails). A player who doesn't participate in the heist has cost 0. Therefore, the payoff of a player who chooses P is 1 if the heist succeeds, and is -1 if the heist fails, while the payoff of a player who chooses N is 2 if the heist succeeds, and is 0 if the heist fails.