And so we could write that as h prime of, we could say h prime of x, but we want the rate when x is equal to 1.8. So h prime of 1.8 is what we want to figure out. Now we could evaluate f prime of 1.8 and g prime of 1.8, and to do that we would take the derivatives of each of these things and we know how to do that. It's within our capabilities. But it's important to realize when you're taking the AP test that you have a calculator at your disposal. And a calculator can numerically integrate and it can numerically evaluate derivatives. And so whenever they actually want us to find the area or evaluate an integral where they give the endpoints or evaluate a derivative at a point, well that's a pretty good sign that you could probably use your calculator here.