n class="n">r_s</span> <span class="o">=</span> <span class="mf">0.5</span> <span class="o">/</span> <span class="n">n</span><span class="p">[</span><span class="n">j</span><span class="p">]</span>
            <span class="n">e_c</span><span class="p">[</span><span class="n">j</span><span class="p">]</span> <span class="o">=</span> <span class="p">(</span>
                <span class="o">-</span><span class="p">(</span>
                    <span class="p">(</span><span class="n">q</span><span class="p">[</s