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:       Would you like to have dinner with me tonight ?  
 Person2:Oh , that sounds great !  
 Person1:        I ’ ll pick you up at ... say , seven thirty ?  
 Person2:Yes , that would be perfect .  
 Person1:        See you tonight then .  
 Person2:Yes . Thank you for inviting me . 

informal