1--Are these books on sale?   

2--The book store is celebrating its fifth birthday,so there is a 35% discount on all books.     

1--Great!       

2--Remember they are only on sale within this week.      

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注解：

1.on sale打折
2.celebratin庆祝
3.within this week本周内

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译文：

1--这些书打折吗？    
2--书店五周年店庆，所有的书都打六五折。      
1--太好了！        
2--记住只是在本周之内打折。