International trade A. must benefit both countries exactly the same amount
B. limits a nation's ability to produce goods and services on its own.
C. allows a nation to consume at a point outside its production possibilities frontier.
D. is based on absolute advantage.​

It's A if anyone is wondering

Its complicated if im correct its confused

You're asking in the ap section, so i'll give the ap calculus-style answer. alternatively, you can find the vertex of the parabola and use the "y"-coordinate as the answer.

the maximum height can occur at a critical number, that is, a number  such that  .

the derivative of  can be calculated as follows:



find a value of  that is a zero of the derivative:


this is parabola that is opening downward; we can assume there is a maximum at  .

to find that maximum, calculate  .