Answer
12,000 dollars
Work Step by Step
$C(x)=2x^2-800x+92000$
Since the graph opens downward, the vertex will have the highest point on the graph.
$a=2$, $b=-800$, $c=92000$
Vertex: $x=-b/2a$
$x=-(-800)/2*2$
$x=800/4$
$x=200$
200 bikes
$C(x)=2x^2-800x+92000$
$C(200)=2(200)^2-800*200+92000$
$C(200)=2*40000-160000+92000$
$C(200)=80000-160000+92000$
$C(200)=12000$
12,000 dollars
