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: In my opinions , someone else has caused the fire of this house .
Person2:Who do you think that has the motive ?
Person1: I ' m not sure now . In any case , let ' s first make some careful investigations .
Person2:OK , murder will out !
Person1: Yeah .
Solution:
formal