Which one of the following statements is true? a. You must have a discount rate to compute, NPV, IRR, PI, and discounted payback. b. Payback uses the same discount rate as that applied in the NPV calculation. c. You must know the discount rate to compute the NPV but you can compute the IRR without having a discount rate. d. Discounted payback is a better method than payback and is more frequently used in practice. e. Financing projects can only ever have one IRR.