(a) In his discretion, the Commissioner may:

(b) For the purpose of any investigation or proceeding under this title, the Commissioner or any officer designated by him may administer oaths and affirmations, subpoena witnesses, compel their attendance, take evidence, and require the production of any books, papers, correspondence, memoranda, agreements, or other documents or records which the Commissioner considers relevant or material to the inquiry.

(d) A person is not excused from attending and testifying or from producing any document or record before the Commissioner, or in obedience to the subpoena of the Commissioner or any officer designated by him, or in any proceeding instituted by the Commissioner, on the ground that the testimony or evidence, documentary or otherwise, required of him may tend to incriminate him or subject him to a penalty or forfeiture. However, an individual may not be prosecuted or subjected to any penalty or forfeiture for or on account of any specific subject concerning which he is compelled, after claiming his privilege against self-incrimination as to that specific subject, to testify or produce evidence, documentary or otherwise, except that the individual testifying is not exempt from prosecution and punishment for perjury or contempt committed in testifying.