Let's say we take the point b right there. And then this coordinate up here is going to be the point b, bf of b. Because this is just the point when you evaluate the function at b. You put b in here, you're going to get that point right there. So let me just draw a little line right there. So that is f of b right there. Actually, let me make it clear that this coordinate right here is the point a, f of a.