Rollins Corporation is estimating its WACC. Its target capital structure is 20 percent debt, 20 percent preferred stock, and 60 percent common equity. Its bonds have a 7.0 percent coupon, paid semiannually, a current maturity of 20 years, and sell for the par value, $1,000. The firm's marginal tax rate is 38 percent.

What is Rollins' component cost of debt? Express your answer in percentage (without the % sign) and round it to two decimal places.