Suppose the position of a particle in motion at time $t$ is given by the vector parametric equation $\vec{r}(t) = \langle 3t, 6t^{3}-3t^{2} \rangle$.

(a) Find the velocity of the particle at time $t$.
$\vec{v}(t)$ =

(b) Find the acceleration of the particle at time $t$.
$\vec{a}(t)$ =