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 morning , sir . May I help you ?  
 Person2:Good morning . I'd like to pay my bill .  
 Person1:        OK . In cash or by credit ?  
 Person2:In cash . How much is the total charge ?  
 Person1:        Five hundred and thirty yuan altogether including charges for service .  
 Person2:Here you are . Thanks for your wonderful service .  
 Person1:        Not at all . Welcome again . 

informal