Total extent only to fix the rates.

For the purposes of this Act, - (i) the total extent of the urban land which is vacant or which is used for residential purposes in an urban area shall be taken into account for applying the rates specified in Parts I and III of the Schedule; (ii) the total extent of the urban land used for non-residential purposes in an urban area shall be taken into account for applying the rates specified in Parts II and IV of the Schedule.