The investment required for the project profitability index should:

a. be reduced by the amount of any salvage recovered from the sale of old equipment.

b. be reduced by the amount of any salvage recovered from the sale of the new equipment at the end of its useful life.

c. be reduced by the amount of any salvage recovered from the sale of both the old and new equipment.

d. not be adjusted for the salvage value of old or new equipment.