Suppose all the petroleum in the world is produced by two countries. Let's call the countries Petropia and Oileana, and let's imagine that Petropia and Oileana cooperate with one another in the sense that each commits to produce and sell a certain quantity of petroleum. Suppose their agreement states that Petropia produces 80 percent of the world's petroleum and Oileana the other 20 percent. Show graphically why Oileana will want to cheat on this agreement but Petropia will not