Three people, A, B, and C, go on an outing. When having lunch, B buys back 3 pieces of bread, and C buys back 5 bags of candy and 1 bag of fresh milk. The fresh milk will be returned to the store by B, leaving the returned money. In the end, A paid C 4 yuan, and everyone thought the apportionment was reasonable. How much is this bag of fresh milk?
甲乙丙三人去郊游，用午餐时，乙买回3个面包，丙买回5包糖果和1袋鲜奶，面包和糖果的单价正好相等，三人分吃面包和糖果只剩下一袋鲜奶，由乙返还商店，留下退回的钱．最后甲付给丙4元，大家认为分摊合理，这袋鲜奶多少元？
<result>0.5</result>