please help me with these question

3.65 Question 16 (5 points) ZigZag company has cost of debt of 8%. Given the 21% corporate tax rate, what is the after-tax cost of debt? \begin{tabular}{|l|} \hline .59% \\ \hline 38% \\ \hline 6.32% \\ \hline 1.68% \\ \hline \end{tabular}