It's going to be pi over two times one minus x over two squared. So it's one minus x over two, over two squared. And so if I wanted a volume of just this disc right over here, I'd then multiply that area times the depth. 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.