Mary needs school supplies. She has 6 classes and needs 1 folder for each class. She also needs 3 pencils for each class. She decides that for every 6 pencils she should have 1 eraser. She also needs a set of paints for an art class.  Folders cost $6, pencils cost $2, and erasers cost $1. If she spends $80, how much did the set of paints cost in dollars?
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