The position of a particle moving along the $x$-axis is given by $s(t) = 3t^{2}+6$. Use difference quotients to find the velocity $v(t)$ and acceleration $a(t)$, filling in the following expressions as you do so:

$v(t) = \lim\limits_{h\to0}$ [ / h ] =

$a(t) = \lim\limits_{h\to0}$ [ / h ] =