Review this CSV as a small USD expense table.
Columns: item, quantity, unit_price. Treat quantity as a count and
unit_price as USD per item. Do not fill missing values silently.

Return:
1. Validation issues, including missing, negative or nonnumeric values.
2. Each valid row's quantity × unit_price.
3. The sum of valid rows, with excluded rows listed separately.
4. The exact formula or short reproducible script used.
5. A distinction between source values and calculated values.

Do not claim the total is verified unless it has been independently
recalculated. CSV: [paste a non-sensitive CSV].
