Well, we're trying to figure out how fast the height of the water is changing with respect to time. We know that the height right now is 2 centimeters, but what we want to figure out is the rate at which the height is changing with respect to time. If we can figure out this, then we have essentially answered the question. So one way that we can do this is that we can come up with a relationship between the volume at any moment in time and the height at any moment in time, and then maybe take the derivative of that relationship, possibly using the chain rule, to come up with a relationship between the rate at which the volume is changing and the rate at which the height is changing. So let's try to do it step by step. So first of all, can we come up with a relationship between the volume and the height at any given moment? Well, we have also been given the formula for the volume of a cone right over here.