The red pencil is 6 cm longer than the blue pencil, and the red pencil is 2 cm shorter than the green pencil. Which color pencil is the longest? Which is the shortest? How many centimeters is the longest pencil longer than the shortest pencil?
红铅笔比蓝铅笔长6厘米，红铅笔比绿铅笔短2厘米，哪种颜色的铅笔最长？哪种最短？最长的铅笔比最短的铅笔长多少厘米？
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