Great Seneca Inc. sells $100 million worth of 27-year to maturity 10.81% annual coupon bonds. The net proceeds (proceeds after flotation costs) are $975 for each $1,000 bond. The firm's marginal tax rate is 40%. What is the after-tax cost of capital for this debt financing? Round the answer to two decimal places in percentage form. (Write the percentage sign in the "units" box) You should use Excel or financial calculator.