If $\vec{a}$ and $\vec{b}$ are unit vectors, the angle between $\vec{a}$ and $\vec{b}$ for $\sqrt{3} \vec{a} - \vec{b}$ to be a unit vector is

Question

If $\vec{a}$ and $\vec{b}$ are unit vectors, the angle between $\vec{a}$ and $\vec{b}$ for $\sqrt{3} \vec{a} - \vec{b}$ to be a unit vector is –

$30^\circ$