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:       Mr . Lee , I was wondering if you and your wife had plans for next Friday night ?  
 Person2:Yes , I think we might be free . What did you have in mind ?  
 Person1:        I've mailed a formal written invitation to your home inviting you to a dinner party at my home .  
 Person2:That sounds great . Is it casual ?  
 Person1:        Actually , we thought it would be fun to have a formal sit-down dinner for the holidays .  
 Person2:That sounds good . It will give my wife a chance to dress up .  
 Person1:        Yes , we've invited four other couples , so it should be a good mix of people .  
 Person2:That sounds wonderful . Will there be anyone there that I know ?  
 Person1:        Oh yes , everyone we are inviting is from our company .  
 Person2:Great ! I'll look forward to it . We'll make sure and check the mail for our invitation . 

informal