And I encourage you to pause the video and try to think about it. Well, if you try to visualize it, you're thinking, okay, the area under the curve f of x above the x-axis from x equals c to x equals c. So this region, I guess we could call it, that we think about it, does have a height. The height here is f of c. But what's the width? Well, there is no width. We're just at a single point. We're not going from c to c plus some delta x, or c plus some even very small change in x, or some other, or c plus some other very small value. We're just saying at the point c. So we really, when we're thinking about area, we're thinking about a, we're thinking about things, we're thinking about how much two-dimensional space you're taking up.