The required expected rate of return on an efficient portfolio is 12%, the risk free rate of return is 2%, the standard deviation of the rate of return of the market portfolio is 16% and standard deviation of the rate of return of the given efficient portfolio is 20%. Assuming that the capital asset pricing model is valid, calculate the required expected rates of return of three investors, call them A, B, and C, whose fractions of their portfolio amounts invested in the market portfolio, M, are given as:

Investor Fraction of Portfolio Amount Invested in M

A 0.6

B 1.2

C 1.8