A dollar per point

A professor was giving a big test one day to his students. He handed out all of the tests and went back to his desk to wait.

Once the test was over the students all handed the tests back in. The professor noticed that one of the students had attached a $100 bill to his test with a note saying "A dollar per  point."

The next class the professor handed the tests back out. This student got back his test and $64 change.