Which one of the following statements is correct concerning capital budgeting? one: a. The positive return on stock investment implies positive NPV. b. If all machines function the same, we can use the NPV method to the best machine even if we have only the ca sh outflows, c. When analyzing several projects with different period, we have to estimate NPV over the greatest common diviso rof all projects' periods. d. We have to use the same discount rate for the prolects we analyze, e. For mutually exclusive projects, both PI and IRR lead to the same conclusion