Who is Master?

Tweet

After a week of hard work, a coal mine worker goes to a bank to cash out his pay. Seing several hundreds dollars notes, he asks one of them "Who is Master, you or me?". "Me! Because you work for me!" replies the note. The man then deposit $100 into his son saving account which the son widraw a day later. Staring to the note, the son asks "Who is Master you or me?". The note says "I dont know, who do think.." Anybody know the answer?