ul class="flat"><li class="flat__item"><a href="../../exercise/4/2.html#ex4.27">4.27</a>, </li><li class="flat__item"><a href="../../exercise/4/2.html#ex4.28">4.28</a>, </li><li class="flat__item"><a href="../../exercise/4/2.html#ex4.29">4.29</a>, </li><li class="flat__item"><a href="../../exercise/4/2.html#ex4.30">4.30</a>, </li><li class="flat__item"><a href="../../exercise/4/2.html#ex4.31">4.31</a></li></ul></aside>
<h2 id="4.2.3" class="anchor">
<a class="anchor__link link" href="#4.2.3" aria-hidden="tr