Detailed Instructions: 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'.
Problem: Person1: I ' m sorry , but I can ' t find the book that you lend me .
Person2:Oh , that ' s alright .
Person1: I must apologize . I ' ll buy you a new one tomorrow .
Person2:No . Please don ' t . I couldn ' t let you do that .
Solution:
informal