Assume CAPM holds. Suppose the required return of market portfolio is 12%, and the risk free rate is 5%. If stock APT with a beta of 0.7 offers an expected return of 9%, then you should:

a) buy stock APT because it is overpriced

b) buy stock APT because it is underpriced

c) short sell stock APT because it is overpriced

d) short sell stock APT because it is underpriced