There are 3 tennis balls in a barrel, and 12 barrels can be contained in a box. If the price of tennis balls per barrel is 6 yuan, how much does a box of tennis balls cost? To answer this question, how much information is in a bucket of tennis balls is useless.
一桶网球有3个，一箱可装12桶，如果每桶网球价格为6元，那么一箱网球要多少钱？要解答这一题目，一桶网球有多少个信息是没有用的．
<result>3</result>