Calculate charge with a single price override

You are billing a customer based on *usage intervals* and a *single temporary price override*. ## Definitions - A usage record is an interval `[start, end)` where `start` is inclusive and `end` is exclusive. - `defaultPrice` is the price per unit time (e.g., per day) when no override applies. - An override is: - `override.period = [overrideStart, overrideEnd)` - `override.price` = the price per unit time during the override period. ## Task Given: - `usageRecords: []Interval` (each `Interval` is `[start, end)`) - `defaultPrice: int` - `override: PriceOverride` Compute the **total charge** across all usage time, where: - Any portion of usage that overlaps `override.period` is billed at `override.price`. - Any portion of usage outside `override.period` is billed at `defaultPrice`. Return the total charge as an integer. ## Notes / Edge cases to handle - Usage may be **fully outside**, **fully inside**, or **partially overlap** the override period. - Assume inputs are valid (e.g., `start < end`, prices are non-negative). - Clarify in your solution whether `usageRecords` can overlap each other; if they can, ensure you do not double-bill overlapping usage time (e.g., by merging first). ## Example (conceptual) If `defaultPrice = 10`, override period is `[2, 6)` with `override.price = 5`, and a usage record is `[1, 4)`, then: - `[1,2)` billed at 10 - `[2,4)` billed at 5