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:       Good evening , sir . What can I do for you ? 
 Person2:Bourbon , please . 
 Person1:        How would you like your Bourbon , straight or on the rock ? 
 Person2:With iced water , please . 
 Person1:        Here you are , sir . Bourbon with iced water . 
 Person2:Thank you . Now how much do I owe you ? 
 Person1:        The bourbon is 15 dollars plus 10 % service charge . So the total is 16.5 dollars . 
 Person2:That is OK . Here is 20 dollars and you can keep the change . 
 Person1:        Thanks a lot . 

informal