Which of the following statements is correct?
a. Under perfect price discrimination, there is no deadweight loss.
b. If a monopoly can separate its buyers into relatively few identifiable markets and pursue a separate monopoly pricing policy in each market, then profit-maximizing price will be higher in markets in which demand is less elastic.
c. Natural monopolies, by definition, exhibit decreasing average costs over a broad range of output levels. Consequently, enforcement of a marginal cost pricing policy would require natural monopolies to operate at a loss.
d. All of the above.