just to add some (hopefully accurate) discussion to cpk and maratikus’ true-to-form good points:
annex, you’re correct that when two NPV profiles cross they have different IRRs, but the presence of different IRRs when coupled with different project lives doesn’t assure the profiles actually will cross…
If two projects are the same size but have different lives, shouldn’t they originate from the same point on the y-axis (i.e. be equal when the cost of capital is zero)? So if this is true, these profiles can’t ever cross and this situation looks a lot like Answer B (i.e. different lives, different IRRs)
Now let’s try out two projects with equal lives but different sizes. They must originate from different points on the y-axis (after all, they’re different sizes and must have different NPVs if they’re not discounted at all). So assuming I’m right (which is a stretch, as we know), can you think of a way to cross these two profiles? The larger project will have a larger IRR and the smaller one will have a smaller IRR, right? Won’t these profiles move basically parallel down towards the x-axis? Granted, I haven’t thoroughly considered messing around with the timing of cash flows. It seems like you’d have to push all the cash flows from the larger project to the very end (to minimize IRR) and have a lot of early cash flow for the smaller project, with a small amount at the very end (to maximize IRR) and maybe get these profiles to cross…
So but if you have two projects with different sizes and different lives, a larger (and likely longer) project starts out higher on the y-axis and slopes more steeply towards the x-axis while the smaller (likely shorter) project starts lower on the y-axis and has a flatter slope towards the x-axis… viola!
Anyway, that’s my $0.02 for now.