Please explain how to solve part 6 in details

Consider the following static Prisoner's Dilemma game. --II 5. Let both players adopt the following strategy: start with cooperation; cooperate if both players cooperated or both players defected in the previous period; defect if one player defeated and another player cooperated in. the previous period. In other words, the punishment for deviating from cooperation only lasts for one period, and both players revert to cooperation immediately after. Is it a SPNE if 6 = 3/5? What if 5 = 1/3? 6. Suppose 5 = 1/4. Before the game starts, you tell the players that you will oer each of them money m > 0 at each period both of them cooperate. At least how much should you offer to make the strategy described in part 5 a SPNE