Which of the following is NOT required when performing subtantive analytical procedures?

a. Develop an expectation of recorded amounts or ratios and evaluate whether the expectation is sufficiently precise.

b. Evaluate the reliability of data from which the auditor's expec-tation of recorded amounts or ratios is developed

c. Determine whether a particular analytical proceure is suitable for testing a given assertion

d. Investigate all differences between recorded amounts and their expected values.