In the figure above, the Lorenz curve that shows the richest 20 of households percent receiving 60 percent of all income is

Which of the following statements is TRUE about the relationship among external, internal and social costs?

A) External cost is the difference between social and internal costs. B) Internal cost is the sum of social and external costs. C) Social cost is the difference between internal and external costs. D) none of the above

Which of the following is a common barrier to entry in a monopoly market?

A. Economic profits greater than zero for the monopolist. B. A vertical supply curve. C. A patent on a new product. D. A rising long-run average total cost curve.