Final answer:
The present value of the interest tax shield that increases the value of DFB is $154 million, which is calculated by finding the present value of the annual tax shield using the formula for the present value of an annuity with a 5% discount rate over 10 years.
Step-by-step explanation:
To calculate how much the interest tax shield increases the value of DFB, we need to calculate the present value of the tax savings from the interest payments. Since DFB is restructuring its existing debt to pay $80 million in interest each year for the next 10 years, with a marginal tax rate of 25%, the annual tax shield is 25% × $80 million = $20 million. The present value of this annual tax shield, discounted at the risk-free rate of 5%, is the sum of the present values of all tax shields over the 10-year period.
Using the formula for present value of an annuity:
PV = C × [(1 - (1 + r)^-n) / r]
Where C is the annual cash flow (tax shield), r is the discount rate, and n is the number of periods:
PV = $20 million × [(1 - (1 + 0.05)^-10) / 0.05]
PV = $20 million × [7.72173]
PV = $154.43 million
Therefore, the interest tax shield increases the value of DFB by $154 million, which corresponds to option B.