A frozen pizza is placed in a hot oven and then removed from the oven after 15 minutes. Suppose that the function P(t) represents the temperature of the pizza, in degrees Centigrade, t minutes after the pizza is placed in the oven. Responding with complete sentences and appropriate units: A. What is the meaning of the derivative, P' (t) ? B. What does P' (5) - 9 mean in this situation? C. Is P' (t) always positive? Or does it change sign? Explain