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:       This website offers very convenient air tickets booking service . It is quick and accurate . 
 Person2:Yes , I once booked there . They give the immediate confirm information and flight information to both your mobile phone and e-mail . You can conveniently pay by credit card , so the whole transaction only takes a couple of minutes . They also provide e-tickets , meaning you don ’ t need to go to any office to pick an air ticket . You go to the airport directly and check in with your ID card . 
 Person1:        So it has attracted more and more customers these days . 
 Person2:Yes , therefore they are expanding the scope of their service . For example , hotels can be booked through the same site as well . 

informal