A woman in a shoe store pays for a pair of $30 shoes with a $50 bill. The clerk doesn't have change so he goes to the shop next door to break the $50. He then gives the woman her change.
A while later the clerk next door comes in complaining that the bill she got from the shoe clerk was counterfeit. The shoe clerk gives the other shopkeeper a $50 bill of his own in apology. Both the woman with the fake bill and the shoes she took are gone. In total, how much did the shoe clerk lose in dollars?