Section 122(2)(a) in The Coimbatore City Municipal Corporation Act, 1981
(a)in the case of-(i)any State Government or railway building; or(ii)any building of a class not ordinarily let the gross annual value, of which cannot, in the opinion of the Commissioner, be estimated, the annual value of the premises shall be deemed to be six per cent of the total of the estimated market Value of the land and the estimated present cost of erecting the building after deducting for depreciation a reasonable amount which shall in no case be less than ten per cent of such costs;