Look at the table Production Possibilities for Machinery and Petroleum. The table shows the number of units of machinery each country would have to forgo in order to produce additional petroleum, assuming constant costs at its current levels of production. Based on the information in the table, it is true that:
A. petroleum costs are the same in the United States and in Mexico.
B. the opportunity cost of petroleum is more in the United States than in Mexico.
C. the opportunity cost of petroleum is less in the United States than in Mexico.
D. machinery costs are the same in the United States and in Mexico.