The set of all $\alpha$, for which the vectors $\vec { a } = \alpha t \hat { i } + 6 \hat { j } - 3 \hat { k }$ and $\vec { b } = t \hat { i } - 2 \hat { j } - 2 \alpha t \hat { k }$ are inclined at an obtuse angle for all $t \in \mathbb { R }$, is\\
(1) $\left( - \frac { 4 } { 3 } , 1 \right)$\\
(2) $[ 0,1 )$\\
(3) $\left( - \frac { 4 } { 3 } , 0 \right]$\\
(4) $( - 2,0 ]$