To help finance a major expansion, Castro Chemical Company sold a noncallable bond several years ago that now has 20 years to maturity. This bond has a 9.25% annual coupon, paid semiannually, sells at a price of $875, and has a par value of $1,000. If the firm's tax rate is 25%, what is the component cost of debt for use in the WACC calculation? Do not round your intermediate calculations.

a. 6.60%

b. 6.47%

c. 7.77%

d. 8.09%

e. 7.30%