And then we want to sum up all of the rings over our interval. So we're going to sum up all of the rings over the interval. And when you take the integral sign, it's a sum where you're taking the limit as you have an infinite number of rings that become infinitesimally small in height or depth, depending on how you view it. And what's our interval? So we've looked at this multiple times. These two graphs, you could do it by inspection. You could try to solve it in some way, but it's pretty obvious that they intersect at, remember, we care about our y interval.