In any investigation brought by the Attorney General pursuant to this Act, no individual shall be excused from attending, testifying or producing documentary material, objects or tangible things in obedience to a subpoena or under order of the court on the ground that the testimony or evidence required of him or her may tend to incriminate him or subject him to any penalty. No individual shall be criminally prosecuted or subjected to any criminal penalty for or on account of (a) any testimony or interrogatory answers given by him or her, or (b) any documentary material produced by him or her, as to which he or she would otherwise have a right not to give or produce by virtue of his or her right against self-incrimination, in any investigation brought by the Attorney General pursuant to this Act; provided no individual so giving testimony or answers or so producing documentary material shall be exempt from prosecution or punishment for perjury committed in so testifying, answering, or producing.