In its December 31, 2023 financial statements, Misty Company estimated allowances for doubtful accounts on its current receivables should be $10.2 million. During 2024, Misty actually wrote off $12.4 million in receivables. Ignoring taxes, Misty would report, in its 2024 financial statements, the additional $2.2 million write-off on receivables as:

1. An unusual item.
2. A prior period adjustment.
3. A retroactive adjustment.
4. A current year's expense.

Thank you.