R$21.$ In BitTorrent, suppose Alice provides chunks to Bob throughout a $30-$second interval. Will Bob necessarily return the favor and provide chunks to Alice in this same interval? Why or why not?

R$22.$ Consider a new peer Alice that joins BitTorrent without possessing any chunks. Without any chunks, she cannot become a top$-$four uploader for any of the other peers, since she has nothing to upload. How then will Alice get her first chunk?