The position of a particle moves along a straight line is defined by s = t³-6t²-15t + 40 where s is

The position of a particle moves along a straight line is defined by s = t³-6t²-15t + 40 where s is measured in m and t is in sec. Determine:
(a) time at which the velocity will be zero
(b) the position and distance travelled by the particle at that time
(c) the acceleration of the particle at that time
(d) the distance travelled by the particle when t = 4 sec to 6 sec.