;</span>two <span  title="" class="an ">&ensp;</span>constituents <span  title="" class="an ">&ensp;</span>at <span  title="" class="an ">&ensp;</span>a <span  title="" class="an ">&ensp;</span>time <span  title="" class="an ">&ensp;</span>while <span  title="" class="an ">&ensp;</span>keeping <span  title="" class="an ">&ensp;</span>the <span  title="" class="an ">&ensp;</span>third <span  title="" class="an ">&ensp;</span>constant <span  title="" class="an ">&ensp;</span>The <span  title="" class="an ">&e