This right over here is our second rectangle that we're going to use to approximate the area under the curve. That's rectangle number 2. Let's do rectangle number 3. Well, rectangle number 3, the left boundary, we're just going to call it x sub 2. And its height is going to be f of x sub 2. And its width is going to be the same width as the other ones. I'm just eyeballing it right over here.