1. Please describe the features of four kinds of market structure,perfect competition, monopoly, oligopoly and monopolisticcompetition. (30 分)

2. The demand and supply functions of two-commodity marketmodel are as follows:Qd1=18-3P1+P2; Qd2=12+P1-2P2;Qs1=-2+4P1; Qs2=-2+3P1,where Qdi is the demand for commodity i, Qsi is the supply forcommodity i, Pi is the price for commodity i. Please find thegeneral equilibrium price and output and for i=1 and 2. (20 分)