Prior to January 1, 1978, the proviso to sub section (l) of section 5 provided that "The State Government may, from time to time by notification. fix a higher rate not exceeding thirteen per cent or any lower rate of tax. " Section S (I) as amended with effect from January, 1978, provides that "The tax shall be levied. at such rate, not exceeding thirteen per cent. as the State Government may, from time to time by notification, specify." Thus, the Power of the State Government to issue notification under these two sections is to be exercised by it "from time to time" and, therefore, the State Government can under section 5(1) issue a notification and repeal and replace it by another notification enhancing or lowering the rate of tax and similarly it can issue a notification under section 3 B declaring particular goods or class of goods to be liable to tax on the turnover of purchases and subsequently by another notification repeal that notification with the result that the particular goods or class of goods will from the date of such repeal be again liable to pay tax on the turnover of sales.