Can you please let us know if you are referring to a specific source (you've placed 1.31 at the beginning)? If this is a practice question from that source, please include the full question and answer. We really need you to be more specific when asking questions, especially if you are referring to a specific source. It is much easier for people to answer questions if they have the full source that you are referring to. Thank you.
Updated to note that I've sent a private message to you because you have posted numerous new threads like this in the forum.