Let \( S = \{ x : x \in \mathbb{R} \text{ and } (\sqrt{3}+\sqrt{2})^{\,x^2-4} + (\sqrt{3}-\sqrt{2})^{\,x^2-4} = 10 \} .\) Then \( n(S) \) is equal to:
\( 6 \)
\( 2 \)
\( 0 \)
\( 4 \)