The A quota of each sugar-producing undertaking referred to in paragraph 1 shall be determined by applying to the average annual quantity of sugar produced by the undertaking concerned during the 1984/85 to 1988/89 marketing years within the meaning of Article 2 (1), hereinafter referred to as the reference production, a coefficient representing the ratio between the basic quantity A referred to in paragraph 2 and the sum of the reference production quantities of the undertakings in the region defined in paragraph 1.