Describe what is meant by acceptable audit risk. Explain why each of the following statements is true:

a$.$ A CPA firm should attempt to achieve the same audit risk for all audit clients when circumstances are similar.

b$.$ A CPA firm should decrease acceptable audit risk for audit clients when external users rely heavily on the statements.

c$.$ A CPA firm should decrease acceptable audit risk for audit clients when engagement risk is high.

d$.$ Different CPA firms should attempt to achieve reasonably similar audit risks for clients with similar circumstances.