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 | 36000   | 2025-10-02 09:09:06 | cash   | 18000  | 18000
3    | 12000 | 36000   | 2025-10-03 20:11:24 | cash   | 18000  | 0
