A tenant may file an application to the Rent Authority for fixing the standard rent of the premises and a landlord or a tenant may file application for determining the lawful increase or decrease of rent or other charges payable,--
         (a) in the case of any premises which was let and in which the cause of action for lawful increase or decrease of rent or payment of other charges arose, before the commencement of this Act, within two years from such commencement;
         (b) in the case of any premises which was let after the commencement of this Act,--
             (i) for fixing the standard rent thereof, within two years from the date on which the premises was let;
             (ii) in any other case, within two years from the date on which cause of action arose:
     Provided that the Rent Authority may entertain the application after the expiry of the said period of two years, if he is satisfied that the applicant was prevented by sufficient cause from filing the application in time.