So the base, B of t of a triangle, is decreasing at a rate of 13 meters per hour. So the rate of change of the base, that is B prime of t, which is equal to dB dt, and they tell us that that is, it's decreasing at a rate of 13 meters per hour. So that would be negative 13 meters per hour. And so the rate of change of the base with respect to time is going to be negative 13. They gave us that. Now A prime of t, this is the rate of change of the area at time t sub zero. Did they give us this?