(1 point) A particle moves along a straight line and its position at time t is given by s(t) = 2t3 21t2 + 72t where s is measured in feet and t in seconds. Find the velocity (in ft/sec) of the particle at the time when the acceleration is 0. velocity = D The particle changes direction twice from positive to negative at time i=0 and from negative to positive at time :{1