Compute the present value of interest tax shields generated by these three debt issues. Consider corporate taxes only. The marginal tax rate is Tc = .35. a. A $1,800, one-year loan at 10%. (Do not round intermediate calculations. Round your answer to 2 decimal places.) Present value $ 57.27 b. A four-year loan of $1,800 at 10%. Assume no principal is repaid until maturity. (Do not round intermediate calculations. Round your answer to 2 decimal places.) Present value $ c. A $1,800 perpetuity at 9%. Present value