Cost of debt using the approximation formula For each of the following $1,000-par- value bonds, assuming annual interest payment and a 40% tax rate, calculate the after-tax cost to maturity using the approximation formula. p9-4 Discount (-) or Coupon Bond Life (years) Underwriting fee premium(+)interest rate 20 16 15 25 $25 40 30 15 20 -$20 +10 -15 Par -60 9% 10 12