So what we need to do is let's test the different endpoints. Let's test the function at the beginning. Let's test the function at the end of the interval. And then let's see if there's any points where the derivative is either zero or the derivative is undefined. And these points where the derivative is either zero or it's undefined, we've seen them before, we call these, of course, critical numbers. And this would be either in either case, actually if we assume that that's happening at the same number, we would call that a critical number. So those are the different candidates.