Suppose a monopolist discovers a way to perfectly price-discriminate. Under this scenario, consumer surplus is. What are the efficiency costs (deadweight loss) ?.

The correct answer is: zero; zero.

Explanation:

If a monopolist discovers a way to perfectly discriminate, it means that the monopolist will charge equal to the willingness to pay from each consumer.

The consumer surplus is the difference between the maximum price a consumer is willing to pay and the price it actually pays.

Since each consumer is paying price equal to its willingness to pay, the consumer surplus will be zero.

There will be no efficiency costs. The monopolist will sell output where the maximum price the consumer is willing to pay is equal to or greater than the marginal cost. So all efficient trades will occur, there will be no efficiency costs.