Find the interval$($s$)$ on which $f$ is increasing and the interval$($s$)$ on which it is decreasing.

$f(x)=\frac{x^3}{3}-\frac{14x^2}{2}+48x$

Select the correct choice below and, if necessary, fill in the answer box$($es$)$ to complete your choice.

A$.$ The function $f$ is increasing on the open interval$($s$),$ and deereasing on the open interval$($s$).$

$($Simplify your answer. Type your answers in interval notation. Use a comma to separate answers as needed.$)$

B$.$ The function $f$ is decreasing on the open interval$($s$),$ and never increasing.

$($Simplify your answer. Type your answers in interval notation. Use a comma to seperiate answers as needed.$)$

C$.$ The function $f$ is increasing on the open interval$($s$),$ and never decreasing.

$($Simplify your answer. Type your answers in interval notation. Use a comma to separate answers as needed.$)$

D$.$ The function $f$ is never increasing or decreasing.