Economics is best defined as the study of how society manages its scarce resources. how to run a business most profitably. how to predict inflation, unemployment, and stock prices. how the government can stop the harm from unchecked self-interest. Your opportunity cost of going to a movie is the price of the ticket. the price of the ticket plus the cost of any soda and popcorn you buy at the theater. the total cash expenditure needed to go to the movie plus the value of your time. zero, as long as you enjoy the movie and consider it a worthwhile use of time and money. A marginal change is one that is not important for public policy. incrementally alters an existing plan. makes an outcome inefficient. does not influence incentives