(a) If the vectors $\vec{a}$ and $\vec{b}$ are such that $|\vec{a}|=3,|\vec{b}|=\frac{2}{3}$ and $\vec{a}\times \vec{b}$ is a unit vector, then find the angle between $\vec{a}$ and $\vec{b}$.OR(b) Find the area of a parallelogram whose adjacent sides are determined by the vectors $\vec{a}=\hat{i}-\hat{j}+3\hat{k}$ and $\vec{b}=2\hat{i}-7\hat{j}+\hat{k}$.