After a certain nation changed its policy from one that banned international trade in wheat to one that allowed international trade in wheat, the nation began importing wheat. As a result, total surplus in the wheat market increased by 
7 million and producer surplus in the wheat market increased by 15 million and producer surplus in the wheat market decreased by $5 million
微观经济学（全英）
章节列表
1. General Overview of Economics282. Principles of Economics353. Circular-Flow Diagram and PPF204. Interdependence and Trade205. Demand and Supply756. Elasticity717. Price Control and Taxation408. CS, PS and the Efficiency of Markets109. Costs of Taxation2510. International Trade3011. Externalities3112. Public Goods and Common Resources2013. The Costs of Production20