Q17. One bill with all its payments and a running balance.   [2 row(s)]
unit | price    | charged  | paid_at             | method | amount   | balance_after
-----+----------+----------+---------------------+--------+----------+--------------
3    | 12000.00 | 36000.00 | 2025-10-02 09:09:06 | cash   | 18000.00 | 18000.00
3    | 12000.00 | 36000.00 | 2025-10-03 20:11:24 | cash   | 18000.00 | 0.00
