Howitzer and electronic calculator: what they have in common

1. Step 1. Howitzer — is a kind of — Cannon. An artillery piece.
2. Step 2. Cannon — uses — Casting. Barrels were cast.
3. Step 3. Casting — is used in — Window glass. The panes were cast in moulds.
4. Step 4. Window glass — is part of — Solar panel. Tempered cover glass.
5. Step 5. Solar panel — is part of — Electronic calculator. Many run on a solar cell.

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