Your firm is going to borrow $20 million by issuing 15-year bonds. Your firm's cost of debt is 7% and its marginal tax rate will remain at 40% for the next 15 years. By how much does the interest tax shield increase the value of your firm if the debt will not be renewed after 15 years? a) $1,400,000 b) $5,100,432 Oc) $8,000,000 d) $8,400,000 e) $12,751,080