Consider the following position function.

$r(t)=($:$5,t^4,e^{-t}$:$),$ for $t0$

$a.$ Find the velocity and the speed $of$ the object.

$b.$ Find the acceleration $of$ the object.

$a.$ The velocity $is$

$,$

The speed $is$

$b.$ The acceleration $is$

$,,$

$.$