Price discrimination is selling a good or service at a number of different prices, and the price differences is not justified by the cost differences. In order to price discriminate, a monopoly must be able to 1. be able to segregate the market, and 2. make sure that buyers cannot resell the original product or services.

Perfect price discrimination is a price discrimination that extracts the entire consumer surplus by charging the highest price that consumer are willing to pay for each unit.

As a result, the demand curve becomes the MR curve for a perfect price discriminator. As a result,  firms  capture the entire consumer surplus and maximize economic profit.