Find the Error — COUNTIF Conflates Case-Distinct Records

A data engineer is reconciling customer records across three CRMs that intentionally use case to distinguish billing entities — Acme, ACME, and acme are three separate vendor accounts that must stay distinct in the dedup pass. Their per-row "duplicate count" formula in column C:

=COUNTIF($A$2:$A$13, A2)

…is reporting 3 for every Acme-cluster row, flagging them all as duplicates of each other. The engineer expected COUNTIF to be case-sensitive and return 1 for the case-unique rows.

The error: COUNTIF (and the rest of the COUNT/SUMIFS family in Excel and Univer) does case-insensitive comparison. Acme and ACME are treated as identical for matching, so any case variants of the same letters get counted together. There is no range_lookup flag to opt into case-sensitivity.

The fix: use EXACT inside a SUMPRODUCT — EXACT is the one comparison function that does true character-for-character (case-sensitive) matching:

=SUMPRODUCT(EXACT($A$2:$A$13, A2) * 1)

EXACT returns TRUE only when both arguments match exactly (including case); *1 coerces the boolean array to numbers; SUMPRODUCT sums them. Now Acme only counts other Acme rows, not ACME or acme.

Your task:

1. In column C (Duplicate Count), write a corrected formula that returns the case-sensitive duplicate count for each customer.
2. The formula must drag-fill from C2 → C13.

Graded cells: C2 (Acme → 2 — there's a true case-matching duplicate at row 4), C3 (ACME → 1 — case-distinct from Acme/acme), C13 (vandelay → 1 — case-distinct from Vandelay at row 12).