Once the window was open, Rachel seemed to relax, though she attributed it more to the cool breeze and fresh air than truly understanding what was going on.  Taking a deep breath, Rachel got back to work on the problems, furrowing her brow and concentrating on the lesson.  She concentrated, doing her best and comparing from the book until it really started to make sense to her, and then she gave Miranda a smile.  "Oh, okay!"<br/><br/>Pointing to a spot on the book, Rachel explained, "So the limit isn't supposed to be a new design, it's a calculation of how much the other line goes up.  When x-squared increases, it seems to go up faster and faster, but that's because the increase is constant.  It's like with a car, how you hold down the gas pedal and it seems to be a constant increase of speed."  She then started working through the problems rather quickly, letting Miranda see and copy if she wanted to.