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:       ... Now , that's all I want to say about world coal reserves . So let's move on to the next topic , renewable resources . There are three things we have to consider when talking about renewable resources . First , sustainability ; second , marketability ; lastly , the reality factor . Let's talk about each point in more detail ... John , would you like to take it from here ?  
 Person2:Certainly . As my colleague just mentioned , sustainability is a major concern when examining the potential output of a resource . Of course , as you can see from the content of our presentation today , with renewable resource , there is a much larger sustainability than with non-renewable resource . 

informal