We define this as u, and we just saw that du is the same thing as dw. So, this could be rewritten as du. And this is one of the basic integrals, so hopefully we've learned. And this is equal to the natural log of the absolute value of u. Or, if you unwind the substitution, this is equal to the natural log of the absolute value of w minus 300. So, let me write this down. So, the left-hand side right over here, and you might be able to do that in your head.