And we actually care about the interval. So let's say that the interval is between this point right over here, where the two points intersect. And let's say between that and x is equal to 4. So let's say that this right over here, so this is x equals 4. So it's going to be just right over here. So this is the interval that we're rotating. We're going to rotate it around y equals 1, not around the x-axis.