The restaurant

John felt a bit hungry, so he decided to visit a restaurant. After eating two hamburgers and drinking a cup of coffee, he called the waitress and placed a $100 bill on the table:

"You can keep the tip if you answer some of my questions..."

The girl looked at him strangely and pointed to the bill: "What is this?"

"Money. Is it anything else?"

"No. Money here must look like this." And she took out a card.

That was quite a shock for John. His mouth opened wide enough to put an egg into.

The waitress asked: "Do you have any money?"

"It seems that... I don't."

"Then you must wash dishes here for three days to pay."