CPA firms performing management consulting services can accept contingent fee contracts when:

a. The amounts are not material in relationship to the audit billings.

b. The consulting services are for clients for whom the auditor does not provide any form of attestation services related to a company's financial statements.

c. The consulting services are nonattestation services for an audit client.

d. The consulting services are derived from a joint contract with an audit client to perform consulting services for an independent third party.

e. All of the above