The height is going to be dy. So the area of one of those little rectangles right over there, say the area of that one right over there, you could view as, let me do it over here, as 15 over y dy. And then we wanna sum all of these little rectangles from y is equal to e all the way to y is equal to e to the third power. So that's what our definite integral does. We go from y is equal to e to y is equal to e to the third power. So all we did, we're used to seeing things like this, where this would be 15 over x dx. All we're doing here is, this is 15 over y dy.