ass="op">-</span><span class="cn">Inf</span>, b.upper<span class="op">=</span><span class="cn">Inf</span>, a.lower<span class="op">=</span><span class="op">-</span><span class="cn">Inf</span>, a.upper<span class="op">=</span><span class="cn">Inf</span>,</span>
<span>     c.lower<span class="op">=</span><span class="op">-</span><span class="cn">Inf</span>, c.upper<span class="op">=</span><span class="cn">Inf</span>, d.lower<span class="op">=</span><span class="op">-</span><span class="cn">Inf</span>, d.upper