You cook a pie in the oven at 450 ^oF. After taking the cooked pie out of the oven in a kitchen that is 70 degrees, you need to allow it to cool (so you won't burn your tongue) before you can eat it. The graph of the temperature of the pie, as well as a few points on the graph of the temperatures at certain times, t, in minutes, is shown below. Estimate the average rate of change in the pie's temperature during the first 10 minutes and describe what it means in the context of the pie's temperature.

Note: Temperature in degree Farenheit.