Let u = i - j -2 k, v =2 i + j - k, v · w =2 and v × w = u +λ v. Then u · w is equal to

Let $\displaystyle \vec{u}=\hat{i}-\hat{j}-2 \hat{k}, \vec{v}=2 \hat{i}+\hat{j}-\hat{k}, \vec{v} \cdot \vec{w}=2$ and $\displaystyle \vec{v} \times \vec{w}=\vec{u}+\lambda \vec{v}$. Then $\displaystyle \vec{u} \cdot \vec{w}$ is equal to