How much money did he lose??
A lady goes to a store and purchases things worth 200 bucks. She gives the shopkeeper(A) a 1000 buck note. The shopkeeper having no change goes to the neighborhood store and asks for change and he gets the same. The lady collects the change i.e 800 bucks alongwith her purchase and leaves the store. However, the other shopkeeper(B) detects the note as a fake note and gives it back to the shopkeeper(A) and inturn shopkeeper(A) gives him a real note. The shopkeeper(A) has incurred loss. But how much did he lose???