凭栏听雨1. ( 5 ) Assumption : US is a large country in importing steel. There is same elastisity both importing demand curve and exporting supply curve.（进口需求曲线和出口供给曲线的弹性相同）。
In free trade, US imported steel 100 tons in the price of $100 per ton. Now US imposed $20 tariff on importing steel, and imported 67tons. Question: what is the gain of US from the importing tariff ? what is the net loss of the whole world ?
2. (10) In free trade , steel price is $1000 per unit, including coke（焦炭） 400 and iron ore（铁矿石）500 .
Before entering WTO, the importing tariffs are 100%, 50% and 50%. After entering WTO, the importing tariffs are reduced to 5% (coke)，6% (iron ore )。
Question: After entering WTO, what will be the tariff rate of steel in order to keep ERP constant ?
（入世后，要保持与入世前相同的有效保护率，钢铁的进口税率是多少？）
V. Answer the following question in details.( 15 for each, totally 30)
