A, B, and C each have some books. A and B have 54 books in total, and B and C have 79 books in total. It is known that the person with the most books among the three has twice as many books as the person with the least books. May I ask: How many books does B have?
甲、乙、丙三人各有一些书，甲、乙共有54本，乙、丙共有79本，已知三人中书最多的那个人书的数量是书最少的人的2倍．请问：乙有多少本书？
<result>3</result>