Brown & Co$.,$ CPAs, is considering entering into a cooperative arrangement with DG Corporation, an audit client. In which instance would the arrangement be prohibited under AICPA rules?

a$)$ The arrangement would be a joint venture to create a new service.

b$)$ The arrangement is material to Brown but not to DG Corporation.

c$)$ The arrangement is not material to either party.

d$)$ The arrangement involves a prime subcontractor relationship.