And just as a reminder, definite integral is a very special type of sum. We're summing up all of these things, but we're taking the limit of that sum as these dy's get shorter, or gets, I guess, squatter and squatter, smaller and smaller. And we have a larger and larger number of these disks. Really, as these become infinitely small and we have an infinite number of disks, so that our sum doesn't just approximate the volume. It actually is the volume at the limit. So to figure out the volume of this entire thing, we just have to evaluate this definite integral in terms of y. And so how do we do that?