Kinematics of motion in a straight line — practice question

Particle $P$ moves along a straight line, begins from rest at point $O$, and is back at rest $16\,\text{s}$ after leaving $O$. If $t\,\text{s}$ has elapsed since it left $O$, the acceleration $a\,\text{m s}^{-2}$ of $P$ is defined by $a = 6 + 4t\quad 0 \leq t < 2,$ $a = 14\quad 2 \leq t < 4,$ $a = 16 - 2t\quad 4 \leq t \leq 16.$ At no instant does the velocity change suddenly.