If a cup of coffee has temperature $95^{\circ} C$ in a room where the temperature is $20^{\circ} C,$ then, according to Newton's Law of Cooling, the temperature of the coffee after $t$ minutes is $$T(t) = 20 + 75e^{-t/50}.$$ What is the average temperature (in degrees Celsius) of the coffee during the first half hour?

Average temperature = degrees Celsius