Although an improvement in technology enables perfectly competitive firms to earn a positive economic profit in the short run, entry by new firms will ensure that those profits are eliminated over time

If televisions are normal goods, a fall in income will

a. Increase the demand for cars b. Decrease the demand for cars c. Have no effect on the demand for cars d. None of the above

The marginal revenue curve for a perfectly competitive firm

A) is downward-sloping. B) is the same as its demand curve. C) is perfectly inelastic. D) is the same as its marginal cost curve.