The door refused to open. It said, "Five cents, please."

He searched his pockets. No more coins; nothing. "I’ll pay you tomorrow," he told the door. Again he tried the knob. Again it remained locked tight. "What I pay you," he informed it, "is in the nature of a gratuity; I don’t have to pay you."

"I think otherwise," the door said. "Look in the purchase contract you signed when you bought this conapt."

- Ubik, Philip K Dick, 1969

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