After$-$tax cost of debt $=$ Yield $-$tax rate

After-tax cost of debt = Yield (1 -tax rate) Example What will be the yield to maturity on a debt that has par value of $1 ,000, a coupon interest rate of 5%, time to maturity of 10 years and is currently trading at $900? What will be the cost of debt if the tax rate is 30%?