Manny Tallents is a CPA and a lawyer. In which of the following situations is Tal- lents violating the AICPA's Rules of Conduct?

a. He uses his legal training to help determine the legality of an audit client's ac- tions.

b. He researches a tax question to help the client make a management decision.

c. He defends his audit client in a patent infringement suit.

d. He uses his legal training to help determine the accounting implications of a complicated contract of an audit client.