Consider the following game played between Adam and Betty. Betty Cooperate Defect Adam Cooperate Defect 10, 10 3, 15 15, 3 4, 4 a. Find the pure strategy Nash equilibrium to this game. b. Suppose the game is repeated once. What is the equilibrium to this repeated game? c. Suppose the game is repeated indefinitely with probability 0.8. Show that both players choosing a grim trigger strategy (Cooperate unless Defect is played by other player, then Defect forever) is a Nash equilibrium to this repeated game. d. What is the lowest probability that the game will be repeated for which the grim trigger can work as an equilibrium