$15)$ You are trying to estimate the cost of debt for a firm. The firm has one bank loan and two bonds outstanding. The bank loan has an interest rate of $6\%.$ The first bond has $2$ years left to maturity and a $5\%$ YTM$.$ The second bond has $11$ years left to maturity and a $7\%$ YTM$.$ What should you use for the cost of debt?

A$.5\%$

B$.6\%$

C$.7\%$

D$.$ Not enough information