Answer:
a. Annual Interest tax shield = Debt * Interest * Tax Rate
Annual Interest tax shield = $35 million *9% *30%
Annual Interest tax shield = $0.945 million
b. PV of tax shield = $35 million *9% *30% / 9%
PV of tax shield = $10.50 million
c. PV of tax shield at 7% = 35million *7% *30% / 7%
PV of tax shield at 7% = $10.50 million