AI for Google Sheets Array Formulas: A Tested Workflow

Write a Google Sheets array formula for a small test sheet.
Locale: English function names, comma argument separators.
Headers: A1=Product code, B1=Quantity, C1=Unit price, D1=Line total.
Formula location: D2. Input rows: 2 through 5.
Rules: return Quantity * Unit price when Product code is present;
preserve a numeric zero; return blank for a completely empty row.
Flag a partially filled row for review instead of hiding it.
Return the formula, the output for each sample row, and an explanation
of array dimensions, blank handling and expansion requirements.
Explain any limitation. Do not overwrite occupied cells.

Replace bracketed fields with your verified inputs.