Graph the Function and Determine the Interval(s) for Which $f ( x ) \geq 0$

Graph the function and determine the interval(s) for which $f ( x ) \geq 0$ .
$$f ( x ) = - x ^ { 2 } + 4 x$$

A) $( - \infty , 0 ] \cup [ 4 , \infty )$
B) $[ 0,4 ]$
C) $( 0,4 )$
D) $( - \infty , 0 ) \cup ( 4 , \infty )$
E) $\{ 4 \}$