Economic indexes whose upward and downward turning points generally precede the peaks and troughs of general business activity are known as

Which of the following sets of goods might, under the right circumstances, be substitutes for an automobile?

A) Buses, trains, planes B) Powerboats, blimps, motorcycles C) Motels, tents, cardboard boxes D) Designer suits, fine wines, fancy homes E) All of the above.

In perfect competition, an economic profit can be earned

a. only in the long run b. only if the firm is efficient c. only in the short run d. never e. always