Assume that two countries, Ghana and South Korea, both have 200 units of resources that could either be used to produce rice or cocoa. In Ghana, it takes 10 units of resources to produce one ton of cocoa and 20 units of resources to produce one ton of rice. So, Ghana could produce 20 tons of cocoa and no rice, 10 tons of rice and no cocoa, or some combination of rice and cocoa between the two extremes.