Given a text T, and several options, according to the question posed in the text T to choose the most appropriate option from the options as the answer, please directly output the most appropriate option, do not need to output the explanation.

Dot. Com has determined that it could issue $1,000 face value bonds with an 8 percent coupon paid semi-annually and a five-year maturity at $900 per bond. If Dot. Com's marginal tax rate is 38 percent, its after-tax cost of debt is closest to:
Option A:6.2 percent.
Option B:6.4 percent.
Option C:6.6 percent.

Answer: C