Which of the following total cost functions suggests the presence of a natural monopoly?

The time period during which a firm's capital is fixed but its labor is variable is called

A) the planning horizon. B) the short run. C) the long run. D) the very long run.

Which of the following causes the production possibilities curve to shift to the right?

A. a famine B. a war C. the depletion of oil reserves D. the development of a new technology that improves productivity