And so how do we evaluate it in this case? Let me color code it in a similar way. So the v function, this outer thing that just takes things to the third power, I'll put in blue. So f prime of x, another way of expressing it, and I'll use it with more of the differential notation. You could view this as the derivative of, well, I'll write it a couple of different ways. You could view it as the derivative of v, the derivative of v with respect to u, I want to get the colors right, the derivative of v with respect to u, that's what this thing is right over here, times the derivative of u with respect to x. So times the derivative of u with respect to x.