17 The payback rule can be best stated as: A) An investment is acceptable if its calculated payback period is less than or equal to some pre-specified number of years. B) An investment should be accepted if the payback is positive and rejected if it is negative C) An investment should be rejected if the payback is positive and accepted if it is negative. D) An investment is acceptable if its calculated payback period is greater than some pre- specified number of years. 18. The discount rate that makes the net present value of an investment exactly equal to zero is the A) Internal rate of return B) Payback period. c) Average accounting return. D) Profitability index, E) Discounted payback period. 19. The internal rate of return (IRR) rule can be best stated as: A) An investment is acceptable if its IRR is exactly equal to its net present value (NPV). B) An investment is acceptable if its IRR is exactly equal to zero. C) An investment is acceptable if its IRR is less than the required retum, else it should be rejected