Calculating closing work in progress requires cost of goods completed Steps:

• Identify opening WIP: $8,900.
• Add prime cost incurred: $360,000.
• Add factory overheads incurred: $11,580.
• Total manufacturing costs available: $8,900 +$360,000 + $11,580 =$380,480.
• Subtract cost of goods completed to find closing WIP (formula: Closing WIP = Opening WIP + Prime cost + Overheads - Cost of goods completed).

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Final answer: Not enough information.