Using the, I guess we could call it the washer method or the ring method, we were able to come up with a definite integral for the volume of this solid of revolution right over here. So this is equal to the volume. And so in this video, let's actually evaluate this integral. So the first thing that we could do is maybe factor out this pi. So this is going to be equal to pi times the definite integral from 0 to 1. And then let's square this stuff that we have right here in green. So 2 squared is going to be 4.