Question: Characterize each of the following as a positive-sum game, a zero-sum game or a negative-sum game.

a. You play a card game in your form room with three other students. Each player brings $5 to the game to bet on the outcome, winner take all.

b. Two nations exchange goods in a mutually beneficial transaction.

c. A thousand people buy $1 lottery tickets with a single payoff of $800.