In the suits hereinafter mentioned, fee shall be computed as follows:—
(a) in a suit for maintenance, on the amount claimed to be payable for one year;
(b) in a suit for enhancement or reduction of maintenance, on the amount by which the annual maintenance is sought to be enhanced or reduced;
(c) in a suit for annuities or other sums payable periodically, on five times the amount 18 claimed to be payable for one year:
Provided that, where the annuity is payable for less than five years, the fee shall be computed on the aggregate of the sums payable:
Provided further that a suit for enhancement of maintenance shall be instituted in a court which will have jurisdiction to receive a suit for maintenance at the enhanced rate claimed and one for reduction of maintenance shall be instituted in a court which will have jurisdiction to receive a suit for maintenance at the rate which is sought to be reduced.