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'.

Person1: Thank you so much for coming tonight . Everybody really enjoyed your performance .
Person2:I'm glad I could help .
Person1: Here's the check . I included a little extra for you .
Person2:You didn't have to do that !
Person1: I know , but you deserve it .
informal