Let the velocity vector $bev(t)=($:$3t^2,-12sin(3t),9$exp$(3t)$:$).$ Compute the acceleration vector $a(t).$

$A.($:$6,108sin(3t),81$exp$(3t)$:$)+($:$2,0,6$:$)$

$B.($:$t^3,4cos(3t),3$exp$(3t)$:$)$

$c.($:$t^3,4cos(3t),3$exp$(3t)$:$)+($:$2,-4,3$:$)$

$D.($:$6,108sin(3t),81$exp$(3t)$:$)$

$E.($:$6t,-(36cos(3t)),27$exp$(3t)$:$)$