So now, let me leave that graph up there, because I think that might be useful. What is the second derivative going to be with respect to time? So I'll write it right over here. D, the second derivative of h with respect to time is going to be equal to, well, the derivative of this first term with respect to time, it's going to be the derivative of this with respect to h times the derivative of h with respect to time. So this is equal to negative 1 4th, that's the derivative of this term with respect to h, and then we want to multiply that times the derivative of h with respect to time. This comes just straight out of the chain rule. And then the derivative of a constant, how does that change with respect to time?