V Sam is cooking a roast. The table below gives the temperature R (t) of the roast (in degrees Celsius), at a few times t (in minutes) after he removed it from the oven. Time t Temperature R (t) (minutes) (C) 0 226.6 10 1 205.6 30 l 157.6 50 119.6 70 61.6 from 0 minutes to 10 minutes. [I C per minute from 50 minutes to 70 minutes. I] C per minute (a) Find the average rate of change for the temperature (b) Find the average rate of change for the temperature