So we could say that this right over here, since dh dt is less than zero, for t is greater than zero, the second derivative of h with respect to t is going to be greater than zero, greater than zero, for t is greater than zero. And so what does that mean? It means that we are, if your second derivative is positive, that means you're concave upward, concave upward, which means slope is increasing, slope increasing, slope increasing, or you could say slope becoming less negative, slope becoming less negative. Now what does that mean? And you could see it intuitively, if the slope is becoming less and less negative, then that means when we approximated what our temperature is at t equals three, we used a really negative slope, when in reality our slope is getting less and less and less negative. So what we would have done is we would have over-decreased our temperature from t equals zero to t equals three. So that would mean that we would have underestimated it.