A monopoly earns total revenue of $5,000 when it sells 500 units of output and total revenue of $5,400 when it sells 600 units of output. Thus, the marginal revenue of the 600th unit is $9.

The effective coordination of social behavior through voluntary exchange depends significantly upon

A) clearly defined property rights. B) such civic virtues as courtesy and tolerance. C) well-established and generally accepted rules regarding behavior. D) all of the above.

In 1900, the average life expectancy in the U.S. was:

a. 32 b. 47 c. 60 d. 68