4. The twelve zodiac signs are divided into four categories: Fire, Earth, Air, and Water, with 3 zodiac signs in each category.
The magic school has 20 students, and their zodiac signs are as follows:
\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|c|c|}
\hline Category & \multicolumn{3}{|c|}{ Fire } & \multicolumn{3}{|c|}{ Earth } & \multicolumn{3}{|c|}{ Air } & \multicolumn{3}{|c|}{ Water } \\
\hline Sign & Aries & Leo & Sagittarius & Capricorn & Taurus & Virgo & Libra & Aquarius & Gemini & Cancer & Scorpio & Pisces \\
\hline Number & 2 & 1 & 3 & 4 & 2 & 0 & 2 & 3 & 1 & 1 & 1 & 0 \\
\hline
\end{tabular}

Now, 8 students are to be selected for a magic competition, with 2 signs chosen from each category. There are
$\qquad$ different ways to select them.
$968$