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4. Cob and Fug are two medieval artisans. Cob produces nutritious bread and Fug produces ale that is relatively free of dangerous pathogens. Each would be better off if they could successfully trade with the other: then both could eat bread AND drink ale. However, both are worried about the possibility that the other will cheat them by absconding with the goods without providing payment in kind. In particular, Cob gets a payoff of 5 and Fug a payoff of 6 if they successfully trade items. If Cob attempts to trade bread honestly and Fug cheats him, Cob gets a payoff of -2 and Fug gets a payoff of 8. If Fug attempts to trade ale honestly and Cob cheats him, Fug gets a payoff of -1 and Cob gets a payoff of 8. If they both simultaneously attempt to cheat each other, the exchange fails, and Cob gets a payoff of 1 (since he can still eat bread) and Fug gets a payoff of 0 (man cannot live by ale alone). 4a Write this game in the normal form. 4b Solve for the pure strategy Nash equilibria in this normal-form game. 4c Now suppose that Cob and Fug are old friends who see each other all the time and who have an ongoing trading relationship, i.e., that the game depicted above is an innitely repeated game. Suppose that Cob and Fug have the same discount factor, 6. For what values of 6 can Cob and Fug sustain trade forever using the Grim Trigger strategy? (Hint: You need to check both players' incentives to deviate!)