The answer is B, I need to solution.

Suppose that the annualised average return over a 10-year period on shares is 12%, and on bonds is 9%. If the average annual inflation rate has been 4% over this period, what is the average real rate of return for each of these asset classes? A. 8% for shares and 5% for bonds B. 7.69% for shares and 4.81% for bonds C. 16% for shares and 13% for bonds D. 16.48% for shares and 13.36% for bonds