Let me just rewrite it, and I'll distribute the negative 1 4th, because it'll be a little bit more straightforward then. So if I write the derivative of h with respect to time is equal to negative 1 4th times our internal temperature, which itself is a function of time, and then negative 1 4th times negative 27, that would be plus 27 over four. Let me scroll down a little bit. 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.