Porter Plumbing's stock had a required return of 14.25% 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.

a. 17.93%

b. 17.63%

c. 18.23%

d. 18.53%

e. 18.83%