JEE Main PAPER - 1

Let $\vec{u}$   be a vector coplanar with the vectors $\vec{a} = 2\hat{i} +3\hat{j} -\hat{k}$   and $\vec{b} = \hat{j} +\hat{k}$  . If $\vec{u}$   is perpendicular to $\vec{a}$   and $\vec{u}\cdot \vec{b} = 24$  , then $|\vec{u}|^2$   is equal to: