If an object moves along the y-axis (marked in feet) so that its position at time x (in seconds) is given by f(x) = 90x - 15x2, find the following. (A) The instantaneous velocity function v = f' (x) (B) The velocity when x = 0 and x = 2 sec (C) The time(s) when v = 0 (A) v(x) = (B) The velocity when x = 0 sec is ft/sec. The velocity when x = 2 sec is ft/sec. (C) The velocity is 0 at x = sec. (Simplify your answer. Use a comma to separate answers as needed.)