Parking meter and plumbing: what they have in common

1. Step 1. Parking meter — evolved from — Vending machine. A payment machine.
2. Step 2. Vending machine — includes — Coffee vending machine. A vending machine.
3. Step 3. Coffee vending machine — has part — Centrifugal pump. A pump supplies the water.
4. Step 4. Centrifugal pump — is part of — Water tower. Filled by pumps.
5. Step 5. Water tower — is part of — Plumbing. Maintaining pressure.

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