Pair of chopsticks and mechanical clock: what they have in common

1. Step 1. Pair of chopsticks — is part of — Chopsticks. Tapering rods.
2. Step 2. Chopsticks — uses — Lever. A third-class lever.
3. Step 3. Lever — is part of — Vending machine. A coin presses a lever that opens the dispenser.
4. Step 4. Vending machine — evolved into — Parking meter. A payment machine.
5. Step 5. Parking meter — has part — Mechanical clock. A clock mechanism.

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