(1) Notwithstanding anything contained in any agreement, where the premises have been let out before the commencement of this Act, the rent thereof shall be liable to be revised according to the formula indicated below:- (a) where the premises have been let out prior to lst January, 1950, it shall be deemed to have been let out on lst January, 1950 and the rent payable at that time shall be liable to be increased. at the rate of 5 5 per annum and the amount of increase of rent shall be merged in such rent after ten years. The amount of rent so arrived at shall again be liable to be increased at the rate of 6 5 per annum in similar manner up to the year of commencement of this Act- (b) where the premises have been let out on or after lst January, 1950, the rent payable at the time of commencement of the tenancy shall be liable to be increased at the rate of 7 5 per annum and the amount of increase of rent shall be merged in such rent after ten years. The amount of rent so arrived at shall again be liable to be increased at the rate of 8 5 per annum in similar manner up to the year of commencement of this Act Illustration :- If the rent was Rs. 100 per month on 1st January, 1950, it shall become Rs. 175/- per month on lst January, 1960. It shall become Rs. 306.30 per month on 1st January, 1970 and Rs. 536.30 per month on 1 st January, 1980. (2) Notwithstanding anything contained in subsection (1), where the period of ten years for merger of increase of rent under sub-section (1) is not- completed upto the year of the commencement of this Act, the rent at the rate of 9 5 per annum shall be increased upto the year of the commencement of this Act and the amount of increase of rent shall be merged in rent. (3) The rent arrived at according to the formula given in sub-sections (1) and (2) shall, after completion of each year from the year of commencement of this Act, again be liable to be increased and paid at the rate of 105 per annum and the amount of increase of rent shall be merged in such rent after ten years. Such rent shall further be liable to be increased at similar rate and merged in similar manner till the tenancy subsists. (4) The rent revised as per formula given under subsection (1) or sub-section (2) shall be payable, after the commencement of this Act, from the date agreed upon between the landlord and the tenant or where any petition is filed in a Rent Tribunal, from the date of filing of such petition.