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:       I am so happy to know that the promotion campaign for our new product is very successful . We just made a record sale this season .  
 Person2:That is very encouraging news . I heard that the marketing department has done a three months research , they sent the feedback information to the research and development center by the end of every month . That is to say , the R & D center redesigned the product twice before it was launched into the market .  
 Person1:        It is not an easy job . How do you like the advertisement for the new product ?  
 Person2:That is the best one I have seen . I am sure our target customers , young people will love it .  
 Person1:        Certainly . 

informal