# 4. Problem $4.1 *$

In the class, 6 students received a grade of 5, 7 received a grade of 4, and 1 received a grade of 3. The teacher told them to form pairs with different grades, where the student with the better grade would explain to the student with the worse grade where they made a mistake.

In how many ways could the students form pairs under this condition? Points for the problem: 9.

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