And in this case, it would be infinitely flat rectangles since we're thinking about dy. So dy would be the height of each of these rectangles. And what would be, in this case, the width or the length of this rectangle right over here? Well, over this interval from y one to y two, our blue function, f of y, takes on larger x values than g of y. So this length right over here, this would be f of y, f of y, this x value, minus this x value, minus g of y. So this is going to be f of y minus g of y, g of y. Well, we know what f of y and g of y are.