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:       When can we expect you for dinner ? Can you come tonight ? 
 Person2:Not tonight . I promised to go to a concert with my sister . 
 Person1:        Well ... How about Friday then ? 
 Person2:That sounds fine . 
 Person1:        Good . Shall we say seven o'clock ? 
 Person2:I'll be there . You're still a fabulous cook , aren't you ? 
 Person1:        That'll be for you to decide . I've got a new dish that I want to try out on you . 
 Person2:I'm ready . I'll look forward to it all Friday ! 

informal