Diagnose coffee-shop profit decline

You run a single-location coffee shop. In August 2025, profit dropped 18% vs July while transactions fell 4% and average check rose 2%. You have these data: POS_transactions(order_id, order_ts, item_name, category, qty, unit_price_cents, discount_cents, tender_type), Inventory(date, item_name, purchase_qty, purchase_cost_cents, waste_qty), Labor_shifts(date, employee_id, role, hours, wage_per_hour_cents), Foot_traffic(date, in_count). A) Build a driver-tree and a variance decomposition attributing the profit delta to: unit volume, price/discounting, product mix, COGS changes, waste, and labor productivity. Specify exact formulas and the effect-ordering method (e.g., Shapley or waterfall) and show how each lever contributed to the 18% drop. B) A competitor opened two blocks away on July 15, 2025. Without an A/B test, design a study to estimate its incremental impact on revenue. State the identification strategy (e.g., DiD with synthetic controls, weather/event controls), data requirements, assumptions, and at least two robustness checks (e.g., placebo pre-trends, event-study plot). C) Propose two fast experiments you can run within two weeks to validate hypotheses (e.g., menu engineering, promo timing) and define margin guardrails and a stopping rule.