The answers to the questions are as follows:
- a. The critical point(s) is/are \( x = 7 \).
- b. The function \( f(x) \) is increasing on \( (7, \infty) \) and decreasing on \( (-\infty, 7) \).
- c. There are no local maxima, but there is a local minimum at a critical point.
Thus, the final answers are:
\[
\boxed{x = 7}
\]
\[
\text{Increasing: } (7, \infty), \text{ Decreasing: } (-\infty, 7)
\]
\[
\text{Local Minimum: } x = 7
\]