Pick your favorite consumer app. a) Explain its monetization model and top two competitors with key differentiators. b) As CEO, define three north-star metrics and five guardrail metrics (with precise formulas and eligible events). c) Propose one product improvement with a falsifiable hypothesis; design the experiment (randomization unit, invariant checks, minimal detectable effect, power, sample size, test horizon, novelty mitigation, and seasonality controls) and how you would make a launch decision.