(4) If a ball is thrown into the air with a velocity of 60 ft/see, its height in feet is given by y = 601 - 164" where & denotes time in seconds. (a) Find the average velocity for the time period beginning when { = 3 seconds and lasting 0.5, 0.1, 0.05, and 0.01 seconds. (b) Estimate the instantaneous velocity when { = 3 seconds