A particle moves according to a law of motion s = f(t), t ≥ 0, where t is measured in seconds and s in feet. f(t) = 0.01t4 − 0.02t3 (a) find the velocity at time t (in ft/s). v(t) = (b) what is the velocity after 1 second(s)? v(1) = ft/s (c) when is the particle at rest? t = s (smaller value) t = s (larger value)