Every choice or option on the production possibilities frontier involves a tradeoff. In other words, some amounts of a commodity must be given up in order to get some more amounts of the other commodity. Due to the limited resources, every decision either about economics or about daily routines has a tradeoff. Thus, all tradeoffs involve a cost, referred as opportunity cost. Opportunity cost is the highest cost of the preferred alternative. Production possibilities frontier (PPF) gives the total supply of a country. Indifference curve (I) represents the total demand of a country.