Times the rate at which the height is changing with respect to time. Times dh dt. And you might be a little confused. You might have been tempted to take the derivative over here with respect to h. But remember, we're thinking about how things are changing with respect to time. So we're assuming we did express volume as a function of height, but we're saying that height itself is a function of time. So we're taking the derivative of everything with respect to time. So that's why the chain rule came into play when we were taking the derivative of h or the derivative of h of t, because we're assuming that h is a function of time.