And it works, the derivative of this is indeed one over x. Now it's not so relevant here because our bounds of integration are both positive. But if both of our bounds of integration were negative, you could still do this by just reminding yourself that this is the natural log of absolute value of x. So this, we could say, is plus the natural log of the absolute value of x. It's not a bad habit to do it, and if everything's positive, well, the absolute value of x is equal to x. And so what is this going to be equal to? This is equal to, let's evaluate everything at four.