But let's think about the volume if f of x is rotated around that axis. And to do that, let's imagine each sliver of that volume. So this is, let me draw a little thing right over here. And you can imagine once this little sliver is rotated, it forms, it forms, or you can imagine this length is the radius of a disk. And so, and just to imagine that, let me draw the entire disk. So if this is rotated around, if this is rotated around, it will become a disk. It will become a disk.