我的理解是5A中算出来的Expected risk premium "ERP"只反应系统性风险beta (ERP = beta*Rf)

而Sharpe中的Rp是total return，包含非系统性风险alpha。根据题中信息，是没办法算出Rp的，所以没办法perform valuation.

ERP = beta*Rf

这个公式我怎么从来没看到过。。。

按照教材的说法，RPi = STD(i)*correlation(i,M)*RPm/STD(M)

而beta = correlation(i,M)*STD(i)/STD(M) ------------Note 1

Note 1

****** given corr(i,M)=cov(i,M)/[STD(M)*STD(i)]

divide both sde by STD(M)

******corr(i,M)/STD(M) = cov(i,M)/[STD(I)*STD(M)^2]

move STD(I) to the left

******STD(I)corr(i,M)/STD(M) = cov(i,M)/STD(M)^2, and the right hand side is the definition of beta