Netflix and Hulu are deciding what to charge for their online streaming services. Each streaming service can choose a price of either $9 or $12 per month. There are 10 million potential customers. Of these 10 million, 1 million are loyal Netflix customers and another distinct 1 million are loyal Hulu customers. The remaining 8 million consumers will choose the streaming service that is charging the lower price. If the prices are the same, the two firms will split the market, 5 million customers each. The marginal cost of providing service for each company is 0.

Question: Now assume this is a repeated interaction where each firm chooses $9 or $12 at the beginning of each month. Describe clearly (in words) possible strategies of each player that could sustain a "cooperative" arrangement in which they price at $12 each month. (In particular, specify how the two companies should "agree" to play the game, and what each would do in case anyone deviates or cheats on the agreement.)