When the computed upper exception rate $($CUER$)$ is greater than the tolerable exception rate $($TER$),$ it is necessary for the auditor to take specific action. Which of the following courses of action would be most difficult to justify?

Write a letter to management which outlines the control deficiencies.

Revise the assessed control risk upward.

Expand the sample size and perform more tests.

Reduce the tolerable exception rate so as to accept the sample results.