Consider the following infinitely repeated model between two firms. Each period, the firms earn profits of 10 if they successfully collude. If a firm deviates from the aggreement, it earns 15 in the period in which it cheats. In each period that the firms compete noncooperatively, they each earn profits of 8 (that is, each firm earns a profit of 8 each period from playing the one-shot non-cooperative Nash equilibrium). Let it be the discount factor of each firm. For what values of ? can the firms sustain collusion, using the threat of non-cooperative Nash equilibrium play every period forever as punishment? (it is insufficient to simply insert numbers into a formula you have memorized).