Save as otherwise provided in this Act, the rate of tax on vacant lands in New Delhi shall be between a minimum of ten per cent. and a maximum of twenty per cent. of the annual value of such lands as may be specified by the Council from time to time:
Provided that the Council may, at any time, specify fixed rates between the minimum and the maximum rates of tax as aforesaid for different areas or for different groups of vacant lands in such area:
Provided further that the Council may also introduce graduated rates of tax within the minimum and the maximum rates of tax as aforesaid on the basis of straight line system or any other system as may be specified by the Council.]