CAPM Q

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Consider two stocks, a and b, in a CAPM model. The expected return for each stock is given by: E[r_a] - r^f = alpha_a + beta_a (E[r_M] - r^f), E[r_b] - r^f = alpha_b + beta_b (E[T_M] - r^f), where alpha indicates the deviation from ideal CAPM return expectations. a: If both stocks are fairly priced according to the CAPM model (i.e. expected returns match what the CAPM model would predict), what must alpha_a and alpha_b be? b: Suppose both stocks are fairly priced and beta_b = 1/2 beta_a. Find E[r_a] in terms of E[r_b]. c: Suppose both stocks are fairly priced and E[r_a] = E[r_M]. What must the value of beta_a be? d: Suppose you compile a portfolio from a and b such that beta_P = 0 (the portfolio has no exposure to market risk). If this portfolio is fairly priced under CAPM, what must the expected return of the portfolio (E[r_p])