Debt Repayment Letter

I need a firm letter addressed to my nephew regarding a debt he owes me. The letter should include:

- Detailed breakdown of the owed amount, including dates and specific amounts
- A firm tone, but not overly aggressive
- An expectation for him to acknowledge the debt and commit to a repayment plan

Ideal skills and experience include:
- Strong writing skills
- Experience with formal debt acknowledgment letters
- Ability to convey firmness without hostility