So now we're saying, well, it's okay if it's not differentiable right at a, or if it's not differentiable right at b. And differentiable just means that there's a defined derivative, that you can actually take the derivative at those points. So it's differentiable over the open interval between a and b. So those are the constraints we're gonna put on ourselves for the mean value theorem. And so let's just try to visualize this thing. So this is my function. That's the y-axis.