(c) $\hat n = \frac{{\overrightarrow A \, \times \overrightarrow B }}{{|\overrightarrow A \, \times \overrightarrow B |}} = \frac{{8\hat i – 8\hat j – 8\hat k}}{{8\sqrt 3 }} = \frac{1}{{\sqrt 3 }}(\hat i – \hat j – \hat k)$
There are two unit vectors perpendicular to both $\overrightarrow A $ and $\overrightarrow B $ they are $\hat n = \pm \frac{1}{{\sqrt 3 }}(\hat i – \hat j – \hat k)$