Find the car's average velocity over first 9 seconds

A car's position in feet t seconds after it starts moving is given by s(t) = 9tvt . The average rate of change in position with respect to time is called average velocity. i) Find the car's average velocity over the first 9 seconds. DO NOT INCLUDE UNITS WITH YOUR ANSWER. ii) Find the car's average velocity from t = 16 to t = 25 seconds. DO NOT INCLUDE UNITS WITH YOU