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 7,00% annual coupon, paid semiannually, sells at a price of $800, 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. Ca. 7.68% Cb. 4.18% Cc. 9.21% Od. 4.60% Ce. 6.90%