$6.)$ An auditor is testing for proper recording of expenses at fiscal year$-$end. The auditor is reviewing payroll, medical supplies, and drug costs. Which of the following scenarios could result in the understatement of drug costs:

a$.$ Three employees have been quarantined for two weeks and did not turn in timesheets.

b$.$ Accounts Payable did not pay a large invoice timely.

c$.$ Pharmacy personnel did not enter the receipt for the last delivery of the month.

d$.$ A large credit received in the month was not applied until the following month.