Section 6(1)(a) in The Bombay City (Inami and Special Tenures) Abolition Rules, 1972
(a)The amount of sale price, estimated price or compensation in respect of sales, leases and acquisitions during the period of 15 years, shall be added together and the total amount found out and the total area in square metres of all the lands so sold, leased or arrived at by dividing such total amount in rupees by the total area in square metres.