Solve the Polynomial Equation $f ( x ) = - x ^ { 4 } + 10 x ^ { 3 } - 36 x ^ { 2 } + 48 x$

Multiple Choice

Solve the polynomial equation. In order to obtain the first root, use synthetic division to test the possible rational
roots.
-The concentration, in parts per million, of a particular drug in a patient's blood x hours after the drug is administered is given by the function
$f ( x ) = - x ^ { 4 } + 10 x ^ { 3 } - 36 x ^ { 2 } + 48 x$
How many hours after the drug is administered will it be eliminated from the bloodstream.

A) 4 hours
B) 12 hours
C) 5 hours
D) 16 hours