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

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

(b) Find the speed of the particle at time $t$.
Speed =

(c) Find the time(s) when the particle is stationary. If there is more than one correct answer, enter your answers as a comma separated list.
$t$ =