Megan is a college student who works as a part-time server in a restaurant. Her usual tip is 20% of the price of the meal. A customer ordered a piece of pie and said that he would appreciate prompt service. Megan fulfilled the customer’s request. The customer’s bill was $8, but the customer left a $100 bill on the table and did not ask for a receipt. Megan gave the cashier $8 and pocketed the $100 bill (so Megan ends up with $92). 

Megan concludes that the customer thought that he had left a $10 bill, although the customer did not return to correct the apparent mistake. The customer had commented about how much he appreciated Megan’s prompt service. Megan thinks that a $2 tip would be sufficient and that the excess is like “found money.” How much should Megan include in her gross income concerning this customer?