Metal particle through a medium

Part A
A small metal particle passes downward through a fluid medium while being subjected to the attraction of a magnetic field such that its position is observed to be s=(15t³−3t) mm, where t is measured in seconds. Determine (a) the particle's displacement from t=2 s to t=4 s, and (b) the velocity and acceleration of the particle when t=5 s.

s(2)=114 mm
s(4)=948 mm

displacement = s(4)-s(2) = 834 mm

v=ds/dt v=45t²-3
a=dv/dt a=90t

v(5)=1122 mm/s 

a(5)=450 mm/s²