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:       We'd like to invite you over for dinner this Friday evening . Can you come ?  
 Person2:This Friday evening ?  
 Person1:        Yes . We hope you'll be able to join us .  
 Person2:Thank you for the invitation . I'll be very happy to go .  
 Person1:        Good !  
 Person2:What time should I arrive ?  
 Person1:        How about 6:00 ?  
 Person2:Fine . See you then . 

informal