Exemption of kerosene duty on net consumption basis for manufacture of linear alkyl benzene and heavy alkylate. Exemption applies to kerosene used in manufacture of linear alkyl benzene or heavy alkylate to the extent that duty exceeds the duty on kerosene net consumed, where net consumption equals kerosene received by the factory minus the mineral oil generated in manufacture and returned by the factory to a declared refinery under the central excise rules.