6. (25 points) (lair-rider the Prisoner's Dilemma game below: --lrl Ill-- (a) If this stage game is played twenty times in a row by the same two players, 1what 1will he the subgame perfect equilibria of the resulting repeated game? (h) Now assume the stage game is inniter repeated. Consider the strat- egy (Call it \"Generous lGrim Trigger," or GGT) that plays C for the rst period and also plays C as long as C has been phiyed by both players in all previous periods. Once D is played by either player, GGT plays C for the number of periods for which both players played C at the beginning of the game and then plays D in every period after that. i. Is there a discount factor 6 such that both players' playing GGT can be supported as a Nash equilibrium? (Make sure to check all relevant conditions.) ii. Is there a discount factor ('5 such that both players' playing GGT can he supported as a subgarne perfect equilibrium? (Make sure to check each different type of subgame.)