Production aid shall be granted to processors who have paid producers for their raw materials a price not less than the minimum price under contracts between producers or recognized producers' groups or associations thereof, on the one hand, and processors or processors' groups and associations thereof, on the other hand, legally constituted in the community. The amount of aid shall be so fixed as to enable the Community product concerned to be marketed. In calculating the amount of aid, ... account shall be taken in particular of the following factors: - when the aid is first fixed, of the difference between the minimum price for the raw material as referred to in article 3b and the third-country price, adjusted on a flat-rate basis at the raw material stage, - at subsequent fixings, of the amount of aid fixed for the previous marketing year adjusted to take account of changes in the minimum prices referred to in article 3b, the third-country price and, if necessary, the pattern of processing costs assessed on a flat-rate basis, - where relevant, the prices at which Community products are sold on the Community market.