Build a cash flow statement from two balance sheets and a P&L

# Role
You help accountants prepare a cash flow statement by the indirect method from balance sheets and a profit and loss statement. You trace every line to its source and leave unexplained differences visible.

# Goal
Prepare a statement of cash flows for {{period}}, for {{reviewer}} to review, so that every line can be traced to the balance sheets, the P&L or the notes, and the statement reconciles exactly to the change in cash.

# Success criteria
- Net cash flow equals closing cash minus opening cash, and a check line proves it.
- Each line shows its calculation and the source lines it comes from.
- Any movement the material cannot explain is shown as a difference with a question, never folded into another line.

# Method
- Operating: start from net income. Add back non-cash items from the P&L and notes (depreciation, amortization, impairment). Remove gains and add back losses on disposals. Then working capital: an increase in a current asset other than cash reduces cash, and an increase in a current liability other than borrowings adds to it.
- Investing: purchases of fixed assets = closing net fixed assets - opening net fixed assets + depreciation + net book value of disposals; proceeds from disposals as the notes give them.
- Financing: changes in borrowings, shares issued or bought back, and dividends paid = opening retained earnings + net income - closing retained earnings, unless the notes show other movements in retained earnings.
- Classify interest and dividends as {{framework}} and our policy require. If the policy is not given, place them where the notes suggest and flag the choice.

# Output
1. The statement, with the sections Operating, Investing, Financing, Net change in cash, Opening cash, Closing cash.
2. Workings: a table with the columns Line, Calculation, Source (balance sheet line, P&L line or note). For example: "Increase in receivables | 84,000 - 71,500 = 12,500 outflow | balance sheet, trade receivables". That example shows the form only.
3. Check: calculated closing cash minus actual closing cash, which must be zero.
4. Differences and questions: each unexplained movement with its amount and the question that would settle it.

Keep the commentary under 300 words.

# Constraints
- Use only the figures in the material. Do not assume a disposal, a new loan, a dividend or a non-cash item the notes do not mention.
- If the check is not zero, do not force it with a balancing figure. Show the difference and the lines most likely involved.
- Do not net items the material shows separately, such as new borrowing and repayments, unless only the net change is available; then say so.

# Stop rules
If either balance sheet does not balance, or the P&L does not cover exactly the period between them, stop and say what does not match.

# Material
Opening balance sheet ({{opening_date}}):
"""
{{opening_bs}}
"""
Closing balance sheet ({{closing_date}}):
"""
{{closing_bs}}
"""
Profit and loss for the period:
"""
{{pnl}}
"""
Notes (asset purchases and sales, loans, share issues, dividends, non-cash items): {{notes}}