COMMON CUSTOMS TARIFF - CUSTOMS DUTIES - SPECIFIC DUTIES EXPRESSED IN UNITS OF ACCOUNT - CONVERSION INTO THE CURRENCY OF THE IMPORTING MEMBER STATE - APPLICATION OF THE RATE OF EXCHANGE CORRESPONDING TO THE PARITY NOTIFIED TO THE INTERNATIONAL MONETARY FUND - GENERAL RULE C.3 - VALIDITY - REDUCTION OF CUSTOMS DUTIES TO THE AMOUNT PAYABLE IN THE CASE OF IMPORTATION INTO THE MEMBER STATE HAVING THE WEAKEST CURRENCY - NOT PERMISSIBLE ( REGULATION NO 950/68 OF THE COUNCIL , AS AMENDED BY COUNCIL REGULATION NO 2500/77 , GENERAL RULE C.3 )