某租车公司拥有汽车100辆，当每辆车的月租金为3000元时，可全部租出，当每辆车的月租金每增加60元时，未租出的车将会增加一辆．租出的车每月需要维护费160元，未租出的车每月需要维护费60元．
（Ⅰ）当每辆车的月租金定为3900元时，能租出多少辆车？
（Ⅱ）当每辆车的月租金为多少元时，租车公司的月收益最大？最大月收益是多少？
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| Look 1 this photo. The 2 name is John. He comes from Canada.He is thirteen. He has two 3 . The one 4 the white dress is Rose. The other one (另一个) in the yellow dress is Mary. Rose and Mary 5 eleven. They look 6 .They are twins (双胞胎). John and his sisters are all students. They have good friends in the school. 7 father and mother are both Enlish 8 . John looks like his father. He is tall and 9 a big head. Rose and Mary 10 look like their father. They look like their mother.They are all nice. | ||||
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