For the function $f ( x ) = \left( x ^ { 2 } - 2 x - 7 \right) e ^ { x }$, let the local maximum value and local minimum value be $a$ and $b$ respectively. What is the value of $a \times b$? [3 points]\\
(1) - 32\\
(2) - 30\\
(3) - 28\\
(4) - 26\\
(5) - 24