The stock is currently selling for $15.25 per share, and its noncallable $1,000 par value, 20 -year, 7.25\% bonds with semiannual payments are selling for $875.00. The beta is 1.25, the yield on a 6-month Treasury bill is 3.50%, and the yield on a 20 -year Treasury bond is 5.50%. The required return on the stock market is 11.50%, but the market has had an average annual return of 14.50% during the past 5 years. The firm's tax rate is 25%. Refer to the data for the Collins Group. What is the best estimate of the after-tax cost of debt? 6.10% 6.75% 7.08% 6.43% 5.80%