Divided into ABC classes, A is the competition class, B is the promotion class, and C is the basic class.

Mingxin's placement exam is a set of papers for Mingxin in each grade. You sign up for the exam first, and then rank it according to your grades. Then you decide for yourself whether to pay for his class. The content of the exam is olympiad. It must be quite difficult for people who have never studied Olympic Mathematics before. It is the same to take the placement exam in any institution. Mingxin is famous in Wuhan, but it is difficult. Generally, you can enter Class A with a score above 40.