Which one of the following statement is incorrect?

a. If projects are of a different scale, the IRR rule may give an incorrect ranking and result in selection of a project with a lower NPV.

b. NPV profile shows the NPV for different values of the cost of capital.

c. If there are negative cash flows after the first positive cash flows from a project, it is impossible for there to be multiple internal rates of return. d. NPV profile is useful if there is some doubt as to the true cost of capital.