Suppose that a farmer has two very different 100-acre plots of land. Suited for growing rice than corn one is very wet as well as better. This land produces 40 bushels of rice per acre of land or 10 bushels of corn per acre. The other plot is dry and better suited for growing corn. It produces 10 bushels of rice per acre or 20 bushels of corn per acre.
The farmer considers four different plans for how he might use the land:
Plan 1: Plant both fields with rice.
Plan 2: Plant the wet field with rice and the dry field with corn.
Plan 3: Plant the wet field with corn and the dry field with rice.
Plan 4: Plant both fields with corn.
Calculate the four combinations of outputs of corn and rice for these 4 plans. Plot them as points in this graph. (It does not matter what order you use to plot points. It'll not be connected by lines. Also, notice that this time, corn is on the vertical axis.)