So let's think about the chain rule. The chain rule tells us, let me rewrite everything else, dv with respect to t is going to be equal to pi over 12 times the derivative of this with respect to t. If we want to take the derivative of this with respect to t, we have something to the third power. So we want to take the derivative of something to the third power with respect to something. So that's going to be, let me write this in a different color, maybe an orange. So that's going to be 3 times our something squared times the derivative of that something with respect to t times dh, let me, I've already used that pink, times dh dt. Let's just be very clear. This orange term right over here, and I'm just using the chain rule.