就是一開始的必要收益率是 R=Rf+1.5X (10%-Rf)后來市場平均收益率變15%.那必要收益率就是R2=Rf+1.5X (15%-Rf)=Rf+1.5X (10%+5%-Rf)=Rf+1.5X (10%-Rf)+7.5%=R+7.5%