Alan is cooking a roast. The table below gives the temperature R (I) of the roast (in degrees Celsius), at a few times t (in minutes) after he removed it from the oven. Time 1' Temperature R (t) (minutes) (0C) 0 193.5 15 166.5 30 130.5 60 73.5 75 22.5 (a) Find the average rate of change for the temperature from 0 minutes to 30 minutes. C per minute (b) Find the average rate of change for the temperature from 60 minutes to 75 minutes. C per minute