And so then we get our third rectangle. And then finally, we have our fourth rectangle, the function evaluated at 2.5. So the function evaluated at 2.5 is the height. So this is f of 2.5. Remember, in each of these, I am just looking at the left boundary of the rectangle and evaluating the function there to get the height of the rectangle. Now that I set it up in this way, what is the total approximate area using the sum of these rectangles? And clearly, this isn't going to be a perfect approximation.