Mikkelson Corporation's stock had a required return of 11.55% last year, when the risk-free rate was 3% and the market risk premium was 4.75%. Then an increase in investor risk aversion caused the market risk premium to rise by 2 percentage points. The risk-free rate and the firm's beta remain unchanged. What is the company's new required rate of return? (Hint: First calculate the beta, then find the required return.) Do not round your intermediate calculations. a. 13.55% O b. 15.15% O c. 11.55% d. 12.15% O e. 9.75%