So given the way that this has been constructed, and we want to take the sum of the areas of these rectangles as an approximation under, as the area under this curve, how would we write that as sigma notation? And I'll get us started, and then I encourage you to pause the video and try to finish it. So the sum of these, the sum of these rectangles, we could say it's the sum of, so we'll have n equals one to four, because we have four rectangles. And I encourage you to, and I encourage you to, to finish this up. Once, actually just write it in terms of the function, use function notation. You don't have to write it out as one plus point oh one times something squared. So I'm assuming you've had a go at it.