42. Service of notice by party or arbitrator.- Any notice required by this Act to be served otherwise than through the Court by a party to an arbitration agreement or by an arbitrator or umpire shall be served in the manner provided in the arbitration agreement, or if there is no such provision, either- (a) by delivering it to the person on whom it is to be served or (b) by sending it by post in a letter addressed to that person at his usual or last known place of abode or business in India and registered under Chapter VI of the Indian Post Office Act, 1898.(6 of 1898.)