The pre-tax cost of debt is yield to maturity of the debt.
The yield to maturity of debt is calculated as -
Yield to maturity = ]Coupon payment + ( Face value - Current price) / Number of years)] / [ ( Face value + Current price) / 2]
Here,
Coupon payment = $ 29.50 (semi-annual, thus 5.9% / 2 * 1000)
Face value = $ 1,000
Price = $ 1,000 * 108% = $ 1,080
Number of years = 12 ( semi-annual, thus 6 years * 2)
Pre-tax cost of debt = [ 29.50 + (1,000 - 1080/12)] / [ (1000+1080)/2 ]
Pre-tax cost of debt = 2.196 %
Annual pre-tax cost of debt = = 2.20 % * 2 = 4.40%
After tax cost of debt = ( 1 - tax rate ) * Annual pre-tax cost of debt
After tax cost of debt = ( 1 - 35%) * 4.40 %
After tax cost of debt = 2.86 %
