Which vector is a unit vector that has the same direction as $($:$6,-2$:$)?$

$($:$1,0$:$)$

$($:$3,-1$:$)$

$\frac{1}{\sqrt[\phantom{2}]{40}}($:$6,-2$:$)$

$\frac{1}{\sqrt[\phantom{2}]{36}}($:$6,-2$:$)$