D=1000, is expected to remain constant forever. Compute the present value of all future tax shields under the following scenarios:

a. Corporate tax rate = 34%, tax on interest income = 28%, tax on equity income = 15%

b. Corporate tax rate = 34%, tax on interest income = 28%, tax on equity income = 28%

c. Corporate tax rate = 34%, tax on interest income = 34%, tax on equity income = 0%

d. Corporate tax rate = 34%, tax on interest income = 40%, tax on equity income = 0%