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:       Can I help you , Madam ?  
 Person2:Yes , I'd like to exchange some US dollars into RIB .  
 Person1:        How much would you like to exchange ?  
 Person2:What's the exchange rate for RIB ?  
 Person1:        It's US 100 for RIB 802 today .  
 Person2:I'd like to exchange 3,000 .  
 Person1:        Fill out this exchange memo , please .  
 Person2:Yes . Here you are .  
 Person1:        Wait a second , please ... These are 24,060 RIB and the receipt , please check them .  
 Person2:All right , thank you so much , good-bye .  
 Person1:        Good-bye . 

informal