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A mother and her young son get into a bus in a small city and sit down. The bus conductor comes to them for their money. The mother says:“I want one ticket to the zoo ”and gives him one Yuan. The conductor looks at the small boy for a few seconds and then says to him, “How old are you, young man?”The mother begins to speak, but the conductor stops her. The boy says: “I am four at home, and two in the buses.” At last the mother has to take fifty fen out of her pocket and gives it to the conductor.