Exercise 2: Two Steps, Each Depending on Multiple Chapters — Possible Solution
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EXAMPLE 1: STEP 2 — SCANNING HER FIRST ITEM
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This single step depends on at least four chapters working together: Chapter 4's camera-scanning component actually decodes the barcode from the video feed; Chapter 3's lookupBarcode Cloud Function (with its barcodeCache check and Open Food Facts fallback) turns that barcode into a real product name and category; Chapter 5's addItem flow is what actually writes the confirmed item to Firestore; and Chapter 11's userId field is what makes that write belong specifically to Maya rather than being a generic, ownerless document. No single one of these chapters could produce this step's outcome alone.

EXAMPLE 2: STEP 4 — AN EXPIRY ALERT
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This step depends on Chapter 7's own query logic (filtering active items by an upcoming expiry threshold) and Chapter 12's deployment work (specifically, codifying that query's required composite index into firestore.indexes.json and deploying it for real). Chapter 7's query alone, without Chapter 12's deployed index, would fail with a permission/index error in a real environment rather than actually returning results - the alert only works in practice because both chapters' work is present together.

WHY THIS WORKS AS AN ANSWER
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It picks two genuinely different steps and, for each, names multiple specific chapters whose work must combine for that step to actually succeed, rather than attributing either step to just one chapter in isolation.