(c)
Given, $\overrightarrow{\mathbf{a}} \bullet \overrightarrow{\mathbf{b}} = 12$
$\Longrightarrow \left| \overrightarrow{\mathbf{a}} \right||\overrightarrow{\mathbf{b}}|$ $cos\ \theta\ = 12$
$\Longrightarrow 10 \times 2 \times \cos{\theta = 12}$
$\Longrightarrow \cos\theta = \frac{3}{5}$
$\therefore\sin\theta = \sqrt{1 - {cos\ }^{2}\theta} = \sqrt{1 - \frac{9}{25}} = \frac{4}{5}$
$Now,\ \$
$|\overrightarrow{\mathbf{a}} \times \overrightarrow{\mathbf{b}}| = |\overrightarrow{\mathbf{a}}||\overrightarrow{\mathbf{b}}|\ sin\ \theta = 10 \times 2 \times \frac{4}{5} = 16$