So here we have a situation where we take our left endpoints, where it is equal to two plus one plus two or five. But we could also look at the right endpoints of our intervals. So this first rectangle here, clearly under-approximating the area over this first interval. Its right endpoint is zero. Zero squared plus one is one. So height of one, width of one has an area of one. Second rectangle here, it has a height of, we look at our right endpoint, one squared plus one is two times our width of one.