An auditor is most likely to make which of the following determinations during the tests of details of balances phase of substantively testing the purchasing process?

Vendor's invoice $641556$ appears to correlate to vendor invoice $64-1556.$

We should confirm whether cllient $778$ made an unusually large purchase of $$5,609\mathrm{.}14.$

Postdoctoral researchers are commonly paid monthly.

This business's activity constitutes $5\%$ of the city$-$wide market.