=+P9–6 After-tax cost of debt Bill William intends to purchase a new racing car. He has decided to borrow money to pay the $500,000 purchase price of the car. He is in the 40% federal income tax bracket. He can either borrow the money at an interest rate of 10% from the car dealer, or he could take out a second mortgage on his home. That mortgage would come with an interest rate of 8%. Interest payments on the mortgage would be tax deductible for Bill, but interest payments on the loan from the car dealer cannot be deducted on Bill’s federal tax return.