Determine the critical points of the function
(1) 79:59
\[
f(x)=\left\{\begin{array}{ll}
x^{3}+6 x^{2} & \text { if } x \leq 0 \\
x^{2}-4 x & \text { if } x>0
\end{array}\right.
\]
in the interval \( [-7,7] \).
\[
\begin{array}{l}
\text { A }(-4,32),(0,0),(2,-4) \\
\text { B }(-7,63),(-4,0),(0,0),(2,0),(7,10) \\
C(-4,0),(0,0),(2,0) \\
\text { D }(-7,63),(0,0),(7,21)
\end{array}
\]