A ball is thrown into the air by a baby alien on a planet in the system of Alpha Centauri with a velocity of 21 ft/s. Its height (in feet) is given by y = 21t - 21t2, where t is measured in seconds. (Round your answer to within three decimal places if necessary, but do not round until your final computation.) a. Find the average velocity for the time period beginning when t = 3 and lasting for the following amounts of time. i. 0.01 s: ft/s 1i. 0.005 s: ft/s 1ii. 0.002 s: ft /s iv. 0.001 s: ft /s b. Estimate the instantaneous velocity of the ball when t = 3. Answer: ft/s