Let λ ∈ R, a =λ i +2 j -3 k, b = i -λ j +2 k. If (( a + b ) ×( a × b )) ×( a - b )=8 i -40 j -24 k, then |λ( a + b ) ×( a - b )|^2 is equal to

Let $\displaystyle \lambda \in \mathbb{R}, \vec{a}=\lambda \hat{i}+2 \hat{j}-3 \hat{k}, \vec{b}=\hat{i}-\lambda \hat{j}+2 \hat{k}$. If $\displaystyle ((\vec{a}+\vec{b}) \times(\vec{a} \times \vec{b})) \times(\vec{a}-\vec{b})=8 \hat{i}-40 \hat{j}-24 \hat{k}$, then $\displaystyle |\lambda(\vec{a}+\vec{b}) \times(\vec{a}-\vec{b})|^2$ is equal to