Which of the following statements is true of a required rate of return?

a. A required rate of return is the expected rate of return at which the net present value is zero.

b. A required rate of return is the discount rate at which the payback period of a project is equal to the expected life of the project.

c. A required rate of return is always equal to the internal rate of return (IRR) of a project.

d. A required rate of return is the discount rate that the IRR must exceed for a project to be considered acceptable.