needed to achieve equilibrium. In this diagram, we can analysis the consumer surplus, producer surplus, and deadweight welfare lost. Consumer surplus means the purchaser's willingness to pay minus the purchaser's actual payment. For example, the price of a cake is 200 yen, but consumers think it should be worth 500 yen, then the consumer surplus is 300 yen. If you want to respect the buyer's preferences, then consumer surplus is a good measure of economic welfare. Also, producer's surplus means the seller's price for selling an item or service minus the seller's cost. For example, if a lm company provides a movie at a cost of 500 yen and the fare is 2000 yen, then the producer surplus is 1500 yen. Producer surplus measures the additional benefits that producers receive. In the diagram of economic equilibrium, if there is a deadweight welfare lost, it means