Find repeat invoices without losing legitimate bills

An invoice import contains exact repeats and a disagreement about one amount. Prepare the accepted invoice count and payable total, with a separate count of unresolved rows.

SOURCE DATA
"supplier","invoice","amount_usd"
"A","100","1000"
"A","100","1000"
"A","101","500"
"B","100","750"
"A","102","200"
"A","102","250"
"B","101","0"

RULES
Use supplier + invoice as the business key. The same invoice number from different suppliers is not a duplicate.
Collapse identical repeated rows to one. If amounts disagree for a business key, hold every row for that key.
Keep a genuine zero invoice. Amounts are whole USD for this fictional exercise.

MY FIGURES
Accepted invoices: __________
Accepted total (USD): __________
Exact repeat rows removed: __________
Rows held for conflict: __________

MY REVIEW NOTE
________________________

METHOD
Group the seven input rows by the two-part business key before adding amounts. A/100 is an exact repeat; B/100 is a different bill.
Move both A/102 rows to an exception note. Choosing either 200 or 250 would hide the disagreement.
Add the four accepted amounts, then reconcile raw rows = accepted invoices + repeated rows removed + held rows.

REFERENCE ANSWERS — try first
Accepted invoices: 4. A/100, A/101, B/100 and B/101 remain.
Accepted total (USD): 2250. 1000 + 500 + 750 + 0 = 2250.
Exact repeat rows removed: 1. Only the second identical A/100 row is removed.
Rows held for conflict: 2. Both A/102 rows are held; 4 + 1 + 2 = 7 source rows.

Summing unique amounts loses valid bills that happen to have the same value. Deduplicate by a declared business key, then inspect conflicting values.

For a real import, agree whether invoice identifiers are case-sensitive and how currency is represented. Add supplier and currency to the key when policy requires it.

Occupational context: O*NET 31.0 Database, USDOL/ETA, Task 2486, occupation 43-3031.00. https://www.onetcenter.org/dl_files/database/db_31_0_csv/task_statements.csv
CC BY 4.0: https://creativecommons.org/licenses/by/4.0/
Original practice material and adaptations by Skill Workbench. USDOL/ETA has not approved, endorsed or tested these additions. O*NET is a trademark of USDOL/ETA.