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:       Thank you very much for everything you have done for me during my stay in China .  
 Person2:And I must thank you again for your generous help .  
 Person1:        The help is mutual . I must thank you to see me off . My wife and I will be looking forward to seeing you . You will come to see us , won't you ?  
 Person2:I promise I will take the first chance to call on you . Please send your wife with my best regards . 

informal