Let $a$ and $b$ be real numbers. It is known that the polynomial
$$f ( x ) = x ^ { 3 } + a x ^ { 2 } + b x + 1$$
is
- increasing on the interval $( - \infty , 1 )$,
- decreasing on the interval $( 1,5 )$,
- increasing on the interval $( 5 , \infty )$.
Accordingly, what is $f ( 2 )$?
A) 0
B) 3
C) 6
D) 9
E) 12