Specify the Lowest Price Across Percentage and Buy-X-Get-Y Discounts

Design a price-calculation procedure that takes transaction records and available discounts, then returns the most favorable permitted price. Discounts include percentage reductions and buy-x-get-y offers. ### Constraints The transaction schema, offer eligibility, stacking rules, repeated-use limits, free-item selection, and rounding policy are unspecified. Clarify them before claiming a unique minimum price. This is a conditional pricing-algorithm discussion, with no invented fixed policy or executable console contract. ### Clarifying Questions - Does buy x get y mean y additional units are free, and can the offer repeat? - Which items qualify, and which items become free if prices differ? - Can percentage and quantity offers stack, and in what order? - Is the best price chosen per line, per product, or for the whole transaction? - At which stage are amounts rounded to the smallest currency unit? ```hint Define what makes two offers compatible Choosing the cheapest option independently for each item is valid only when eligibility and usage constraints do not couple the choices. ``` ### What a Strong Answer Covers - Explicit pricing semantics and separation of eligibility from discount evaluation. - A conditional algorithm that actually finds the optimum under its stated assumptions. - Quantity boundaries, rounding, interactions, and validation of a reproducible result. ### Follow-up Questions - What changes if a promotion can be used only once across the whole basket? - How would you explain which offer produced the selected price?