1) If the payoffs in the Prisoners Dilemma are

Unilateral defection = 7
Mutual Cooperation = 5
Mutual defection = 2
Unilateral Cooperation = 1

How patient do the players need to be to be willing to cooperate if they are both playing Permanent Retaliation?

2) If the payoffs in the Prisoners Dilemma are

Unilateral defection = 9
Mutual Cooperation = 6
Mutual defection = 2
Unilateral Cooperation = 1

How patient do the players need to be to be willing to cooperate if they are both playing Tit for Tat?