So we could rule out that one, and we can rule out that one right over there. So now let's think about whether it is differentiable. So differentiability, so differentiability, I'll write differentiability, ability. Did I, let's see, that's a long word, differentiability. All right, differentiability, what needs to be true here? Well we have to have a defined limit as x approaches one for f of x minus f of one over, oh let me be careful, it's not f, it's g. So we need to have a defined limit for g of x minus g of one over x minus one. And so let's just try to evaluate this limit from the left and right-hand sides.