$S ( x ) = - x ^ { 3 } + 6 x ^ { 2 } + 288 x + 4000,4 \leq x \leq 20$

Multiple Choice

$S ( x ) = - x ^ { 3 } + 6 x ^ { 2 } + 288 x + 4000,4 \leq x \leq 20$ 0 is an approximation of the number of salmon swimming upstream to spawn, where x represents the water temperature in degrees Celsius. Find the temperature that produces the
Maximum number of salmon.

A) $12 ^ { \circ } \mathrm { C }$
B) $4 ^ { \circ } \mathrm { C }$
C) $8 ^ { \circ } \mathrm { C }$
D) $20 ^ { \circ } \mathrm { C }$