So the volume of this disk is going to be our depth, dx, times the area of the face. The area of the face is going to be pi times the radius squared. The radius is going to be equal to the value of the outer function. In this case, it's square root of x. So it's going to be pi times our radius squared, which is pi times square root of x squared. And so if we want to find the volume of the entire outer thimble or truffle or whatever we want to call it, before we even carve out the center, we just take a sum of a bunch of these disks that we've created. So that's one disk.