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<b>consider </b><font color="Maroon">u</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">W</font>;<br/>
<a NAME="E2:24_1_1"/>
<span class="p1"><a href="classes2.html#K1">{</a><span class="default"><font color="Maroon">u</font></span><a href="classes2.html#K1">}</a></span> is  non <a href="xboole_0.html#V1">empty</a>  <a href="subset_1.html#M1">Element</a> of <font color="Maroon">W</font>
 
;<br/>
<b>hence </b><a NAME="E3:24_1_1"/>
not for <font color="Olive">b<sub>1</sub></font> being   <a href="subset_1.html#M1">Element</a> of <font color="Maroon">W</font> holds  <font color="Olive">b<sub>1</sub></font> is <a href="xboole_0.html#V1">empty</a>
 ;<br/>


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