(c)
$A \cap B = \{ 2,\ 4\}$
$\left\{ A \cap B \right\} \subseteq \left\{ 1,\ 2,\ 4 \right\},\ \left\{ 3,\ 2,\ 4 \right\},\ \left\{ 6,\ 2,\ 4 \right\},\ \left\{ 1,\ 3,\ 2,\ 4 \right\},\$
$\left\{ 1,\ 6,\ 2,\ 4 \right\},\ \left\{ 6,\ 3,\ 2,\ 4 \right\},\ \left\{ 2,\ 4 \right\},\ \{ 1,\ 3,\ 6,\ 2,\ 4\} \subseteq A \cup B$
$\Rightarrow \ \ \ n(C) = 8$