And that's going to give us the volume of our upside down gum drop type looking thing. So the key here is, so that we can start evaluating the double integral, is to just figure out what the area of each of these disks are as a function of y. And we know that area is a function of y. It's just going to be pi times radius as a function of y squared. So the real key is what is the radius as a function of y for any one of these y's. So what is the radius as a function of y? So let's think about that a little bit.