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:       Betty and I will throw a dinner party this weekend , we ’ d like you to come .  
 Person2:That would be very nice . Only that I ’ ll be a little late . Is that OK ?  
 Person1:        Sure . We ’ ll be looking forward to that day .  
 Person2:So will I . Thank you . 

informal