(a) Subject to the provisions of this Act, the parties are free to agree on the procedure to be followed by the arbitral tribunal in conducting the proceedings.
     (b) If the parties do not reach an agreement, the arbitral tribunal may, subject to the provisions of this Act, conduct the arbitration in a manner that it considers appropriate. The power conferred upon the arbitral tribunal includes the power to determine the admissibility, relevance, materiality, and weight of any evidence.