Well, just like the last video, we would still take a disk just like this, but what is the height of the disk now? Well, the height of the disk is not just x squared, we've generalized it. It is going to be whatever the value of our function is at that point. So the height of the disk is going to be f of x. The area of the space of this disk is going to be pi times our radius squared. So our radius is f of x, and we are just going to square it. That's the area of this face right over here.