That would be another rectangle. This should be reminiscent of a Riemann sum. In fact, that's where the Riemann integral comes from, taking a Riemann sum where you have an infinite number of these rectangles where the width of each of the rectangles, this is how I conceptualize it, is dx. And the height of this rectangle is the function evaluated at an x that's within this interval right over here. And so this part right over here is the area of one of those rectangles and we're summing them all up. And this is kind of an elongated s reminiscent of a sigma for summing. We're summing up the infinite number of those infinitely thin rectangles or the areas of those infinitely thin rectangles between 1 and 4.