Answer:
A. $12
Step-by-step explanation:
For a quadratic of the form ax²+bx+c, the axis of symmetry is given by ...
x=-b/(2a)
For your quadratic function, the axis of symmetry is ...
s = -(2400)/(2(-100)) = 12
The function has its extreme value on the axis of symmetry. Here, the leading coefficient is negative, so the parabola opens downward. That means the extreme value is a maximum.
Profit will be a maximum at a selling price of $12.