If an object moves along the y axis (marked in feet) so that its position at time x (in seconds) is given by the indicated functions in Problem, find
(A) The instantaneous velocity function v = f(x)
(B) The velocity when x = 0 and x = 3 seconds
(C) The time(s) when v = 0
f(x) = x3 - 9x2+ 24x