It is a critical point or critical value for our original function g. So, and that's the only place where g prime is equal to zero. Are there any other points where g prime is undefined? And there have to be points within the domain. So let's see, what would make this undefined? Two x to the x, that you can evaluate for any x. Natural log of x, once again, is only going to be defined for x greater than zero. But that's, we've already restricted ourselves to that domain.