Math question- velocity

5. (6 pts) A student dropped a textbook from the top floor of his dorm and it fell according to the formula s(t) = -16t2 + 8vt, where t is the time in seconds and s(t) is the distance in feet from the top of the building. (a) Write a formula for the average velocity of the ball for t near 4. (b) Find the average velocity for the time interval beginning when t = 4 with duration 1 seconds, 0.5 seconds, and 0.05 seconds. c) What is your estimate for the instantaneous velocity of the ball at t = 4