求翻译：2002年6月24日，买方向卖方发出了愿意购买6台用于包装零售500克至1公斤的干散货商品的机器的要约邀请。2002年7月3日，卖方以回函的形式，对买方的要约邀请的机器的型号和价格以及交货条件发出正式要约。2002年7月12日，买方回复了卖方的要约，并对机器型号、价格、支付方式等进行了详细的承诺。也就是说，2002年7月12日，是双方当事人进行多次接触与磋商达成合同的日期。自该日起合同依法成立有效，受法律保护，双方当事人必须严格按照合同约定履行各自义务。是什么意思？

June 24, 2002, issued a willing buyer to the seller to purchase six used for packaging retail 500-1 g of dry bulk commodities solicitation machine. July 3, 2002, the seller to write back in the form of an invitation to the buyer of the machine models and prices, and delivery conditions to issue a fo

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On June 24, 2002, buy seller willing to buy 6 were issued for retail packaging from 500 g to 1 kg of dry bulk commodity machines of an offer or an invitation. On July 3, 2002, the seller sent a form, an offer or an invitation to buyer the model numbers and prices, and conditions of delivery of the m

On June 24, 2002, buy seller willing to buy 6 were issued for retail packaging from 500 g to 1 kg of dry bulk commodity machines of an offer or an invitation. On July 3, 2002, the seller sent a form, an offer or an invitation to buyer the model numbers and prices, and conditions of delivery of the m