Let $a \in \{-6, -4, -2, 2, 4, 6\}$ be the leading coefficient of a real-coefficient cubic polynomial $f(x)$. If the graph of the function $y = f(x)$ intersects the $x$-axis at three points whose $x$-coordinates form an arithmetic sequence with first term $-7$ and common difference $a$, how many values of $a$ satisfy $f(0) > 0$?\\
(1) 1\\
(2) 2\\
(3) 3\\
(4) 4\\
(5) 5