I'd just multiply the area times this depth here. And we could call that dx, or we could call that delta x. So we could call the depth there delta x. Now, that's the, actually let me be clear. That's the area, the volume, the volume of one of those shells is going to be equal to, and I'll just write this in one color. It's going to be pi over two times one minus x over two squared times the depth, the area times the depth. So this is volume of one of these half discs.