Spreadsheet and fuel cell: what they have in common

1. Step 1. Spreadsheet — uses — Personal computer. It ran on the Apple II.
2. Step 2. Personal computer — has part — Hard disk drive. A hard disk.
3. Step 3. Hard disk drive — is made of — Cobalt. The magnetic layer is a cobalt alloy.
4. Step 4. Cobalt — is material for — Cathode (lithium metal oxide). LiCoO₂ contains cobalt.
5. Step 5. Cathode (lithium metal oxide) — is part of — Fuel cell. A cathode for oxygen.

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