And you just use it, you're taking the derivative of the green function with respect to the blue function. So it's going to be one over the natural log of four, natural log of four, times, instead of putting an x there, it would be times u of x. Times u of x. And of course, that whole thing times u prime of x. And so, and I'm doing more steps, just hopefully so it's clearer what I'm doing here. So this is one over the natural log of four. u of x is x squared plus x.