Failed exams

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Here is a typical set theory problem

Puzzle

An examination in three subjects, Algebra, Biology, and Chemistry, was taken by 41 students. The following table shows how many students failed in each single subject and in their various combinations.

Subjects: A B C AB AC BC ABC
Failed: 12 5 8 2 6 3 1

How many students passed all three subjects?

Help

Hint
The answer is not 4.