Exercise 1: A Chained Dependency — Possible Solution
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SETUP
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    STORY_C_EFFORT = 4
    Story C depends on Story B (which, in the dependent scenario,
    depends on Story A).

RESULTS
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    DEPENDENT chain (C depends on B depends on A):
      A finishes day 12, B finishes day 17, C finishes day 21

    INDEPENDENT (B and C independent of A's own blocker, but C still
    genuinely depends on B):
      A finishes day 12, B finishes day 5, C finishes day 9

    Story C finish day: dependent=21, independent=9
    Delay avoided: 12 days

WHY THIS WORKS AS AN ANSWER
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The 12-day delay is identical to the chapter's own Story B finding,
just inherited one link further down the chain - Story C never
touched Story A's own blocker directly, but because C depends on B and
B depends on A in the dependent scenario, A's own 4-day blocker
propagates through both links. This is the real danger of a dependency
CHAIN rather than a single dependency: the cost of one blocker doesn't
stay contained to the story it directly affected, it compounds onto
every story built to depend on it, however many links away. Making
Story B independent of Story A (as this chapter's own INVEST material
recommends) breaks the chain at its first link, and every story
downstream of B - including C - benefits automatically, without C
itself needing any special handling.