Which of the following correctly define the internal rate of return: a) maximum rate of return a firm expects to earn on a project. b) Rate of return a project will generate if the project in financed solely with internal funds. c) Discount rate that causes the profitability index for a project to equal zero. d) Discount rate which causes the net present value of a project to equal zero. e) Discount rate that equates the net cash inflows of a project to zero.