(a)Waiver of presence of the parties. The Immigration Judge may, for good cause, and consistent with section 240(b) of the Act, waive the presence of the alien at a hearing when the alien is represented or when the alien is a minor child at least one of whose parents or whose legal guardian is present. When it is impracticable by reason of an alien's mental incompetency for the alien to be present, the presence of the alien may be waived provided that the alien is represented at the hearing by an