Which at the following use cases should be solved using Discounts functionality?

The best use case for utilizing the Discounts functionality in Salesforce Industries CPQ is to manage quantity-based discounts. This functionality allows for automatic application of discounts when the quantity of a product ordered reaches certain thresholds. This is particularly useful for incentivizing bulk purchases and efficiently managing pricing adjustments based on volume, which is common in both B2B and B2C scenarios.