It hits zero right over there. So the derivative might look something like this over that interval. Now, the slope of the tangent line is getting more and more and more and more negative, right, until about that point. So it's getting more and more and more negative until about that point. And now it looks like it's getting less and less and less and less negative, all the way until the derivative goes back to being zero. And then it looks like it's getting more and more and more and more positive. So the derivative of this magenta curve looks like an upward-opening U.