If \( [x] \) be the greatest integer less than or equal to \( x \), then \( \displaystyle\sum_{n=8}^{100} \left[ \frac{(-1)^{n} \, n}{2} \right] \) is equal to:
\( -2 \)
\( 0 \)
\( 2 \)
\( 4 \)