A.边际收益曲线低于需求曲线B.需求曲线和边际收益曲线重合C.边际成本为0D.边际收益曲线是一条水平线
A.小于0B.大于0C.等于0D.为最大值
A.PA =PB =MCB.MRA =MRBC.MRA =MRB =MCD.(MRA -MRB)=(1-MC)