Let a =- i + j +2 k, b = i - j -3 k, c = a × b and d = c × a. Then ( a - b ) · d is equal to:

Let $\displaystyle \overrightarrow{\mathrm{a}}=-\hat{i}+\hat{j}+2 \hat{k}, \overrightarrow{\mathrm{~b}}=\hat{i}-\hat{j}-3 \hat{k}, \overrightarrow{\mathrm{c}}=\overrightarrow{\mathrm{a}} \times \overrightarrow{\mathrm{b}}$ and $\displaystyle \overrightarrow{\mathrm{d}}=\overrightarrow{\mathrm{c}} \times \overrightarrow{\mathrm{a}}$. Then $\displaystyle (\overrightarrow{\mathrm{a}}-\overrightarrow{\mathrm{b}}) \cdot \overrightarrow{\mathrm{d}}$ is equal to :