So we're going to take the sum of all of those washers and take the limit as we have smaller and smaller depths and we have an infinite number of infinitely thin washers. So we're going to take the integral over our interval from where these two things intersect, the interval that we care about. It doesn't have to be where they intersect, but in this case, that's what we'll do. So let's say x equals a to x equals b, although it could have been from, this could have been a, that could have been b, but this is our interval. We're saying in general terms from a to b. And this will give our volume. This right over here is the volume of each washer, and then we're summing up all of the washers and taking the limit as we have an infinite number of them.