Exercise 1: A Third Suite Mix — Possible Solution
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SETUP
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    unit_per_test = 0.34 microseconds (measured in the chapter)
    integration_per_test = 0.01 seconds (given for the extrapolation)
    e2e_per_test = 50.27 milliseconds (measured in the chapter)

    Suite C: 100 unit / 100 integration / 130 e2e, 330 tests total

CALCULATION
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    suite_c = 100 * unit_per_test + 100 * integration_per_test + 130 * e2e_per_test
            = 7.54 seconds

RESULTS (all three suites, same 330 total tests)
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    Suite A (300 unit / 25 integration / 5 e2e):    0.50s
    Suite B (30 unit / 50 integration / 250 e2e):   13.07s
    Suite C (100 unit / 100 integration / 130 e2e):  7.54s

    Suite C is 15.0x slower than Suite A
    Suite C is 1.7x faster than Suite B

Suite C sits between the two extremes, exactly where its own mix would
suggest - more e2e tests than Suite A but far fewer than Suite B.

WHY THIS WORKS AS AN ANSWER
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This confirms the chapter's own per-test costs generalize cleanly to
any mix, not just the two specific suites the chapter itself measured
- runtime scales linearly with how many tests sit at each level,
multiplied by that level's own real per-test cost. The exact ranking
(Suite C between A and B) is not a coincidence of these particular
numbers; it follows directly from Suite C's own e2e count (130) sitting
between Suite A's (5) and Suite B's (250).