Porter Plumbing's stock had a required return of 15.00% 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. 19.00%

b. 18.50%

c. 19.50%

d. 20.00%

e. 20.50%

I am getting 15.36% please help to understand what is the correct answer. Thank you