So that's a, and then this is b right over here. And so let's say our function looks something like this. Let's say it looks something, draw an arbitrary function right over here. Let's say my function looks something like that. So this point right over here, the x-value is a, and the y-value is f of a. F of a, this point right over here, the x-value is b, and the y-value, of course, is f of b. F of b. F of b. So all the mean value theorem tells us is if we take the average rate of change over the interval, that at some point, the instantaneous rate of change, at least at some point in this open interval, the instantaneous change is going to be the same as the average change. Now what does that mean visually?