Porter Plumbing's stock had a required return of 13-75% last year, when the risk-free rate was 5.50% and the market risk premium was 4.75%. Then an increase in investor risk aversion caused the market risk premium to rise by 2%. 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.) Select the correct answer. O a. 17.22% O b. 16.02% O c. 16.42% d. 16.82% e. 17.62%