General Motors has a beta of 1.30 and the U.S. T-bill rate is 3.50%. The annual return on the stock market during the past 3 years was 15.00%, but investors expect the annual future stock market return to be 13.00%. Based on the SML, what is the firm's required return ? a. 13.81% b. 14.19% c. 14.72% d. 15.18% e. 15.85%