Definition: You are given a conversation between two people. 'Person1:' and 'Person2:' are used to separate their respective dialogues. You are required to assign a label 'formal' if there is an absence of emotion and a presence of questions anywhere within the conversation. If such pattern is not found assign the label 'informal'.
Input:  Person1:       I ’ m sorry , but I can ’ t find the book that you lend me .  
 Person2:Oh , that ’ s alright .  
 Person1:        I must apologize . I ’ ll buy you a new one tomorrow .  
 Person2:No . Please don ’ t . I couldn ’ t let you do that . 

informal