Suppose that in the British compound of a prisoner of war (POW) camp, the price of cheese is 12 cigarettes per cheese ration and the price of coffee beans is 3 cigarettes per coffee ration. In the French compound, the price of coffee beans is 30 cigarettes per ration.
A british prisoner could exchange his cheese ration for 24 cigarettes, then exchange the cigarettes for 4 coffee rations in the british compound. If he travels to the french compound, he could exchange the coffee for____cigarettes.