$\text { Find the open interval(s) on which } f ( x ) = - 2 x ^ { 2 } + 12 x + 8 \text { is increasing or decreasing. }$

Multiple Choice

$\text { Find the open interval(s) on which } f ( x ) = - 2 x ^ { 2 } + 12 x + 8 \text { is increasing or decreasing. }$

A) increasing on $( - \infty , 6 )$ ; decreasing on $( 6 , \infty )$
B) increasing on $( - \infty , 16 )$ ; decreasing on $( 16 , \infty )$
C) increasing on $( - \infty , 32 )$ ; decreasing on $( 32 , \infty )$
D) increasing on $( - \infty , 24 )$ ; decreasing on $( 24 , \infty )$
E) increasing on $( - \infty , 3 )$ ; decreasing on $( 3 , \infty )$