The power to rule on the jurisdiction of arbitral tribunal rests with?

As per s.16 of the Act. S. 16. Competence of arbitral tribunal to rule on its jurisdiction.—(1) The arbitral tribunal may rule on its own jurisdiction, including ruling on any objections with respect to the existence or validity of the arbitration agreement, and for that purpose,— (a) an arbitration clause which forms part of a contract shall be treated as an agreement independent of the other terms of the contract; and (b) a decision by the arbitral tribunal that the contract is null and void shall not entail ipso jure the invalidity of the arbitration clause.