Let a = i + j + k, c = j - k and a vector b be such that a × b = c and a · b =3. Then | b | equals:

Let $\displaystyle \overrightarrow{\mathrm{a}}=\hat{i}+\hat{j}+\hat{k}, \overrightarrow{\mathrm{c}}=\hat{j}-\hat{k}$ and a vector $\displaystyle \overrightarrow{\mathrm{b}}$ be such that $\displaystyle \vec{a} \times \vec{b}=\vec{c}$ and $\displaystyle \vec{a} \cdot \vec{b}=3$. Then $\displaystyle |\overrightarrow{\mathrm{b}}|$ equals :