In 1997 and 1998, an auditor found that approximately 4 percent of processed sales invoices were not mathematically accurate. In late 1998, the client implemented a control requiring that all sales invoices be extended by two independent employees.

When planning the 1999 engagement, the auditor estimated a 4 percent error rate for processed sales orders. This is an example of which heuristic?

a. Availability.

b. Anchoring-and-adjustment.

c. Representativeness.

d. Base rate neglect.

Choose the correct answer.