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:       Are you free on Friday evening because we were wondering if you would like to come round for dinner ? 
 Person2:Oh , thank you very much . I ’ d like to come , but I ’ m afraid I ’ m busy that evening . 
 Person1:        That ’ s a pity ! Then when would it be a good time for you ? 
 Person2:Well , I ’ m not too sure , actually . I ’ Ve got a lot going on the next couple of weeks . Why don ’ t I call you later ? 
 Person1:        Okay , that ’ s fine . 

informal