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<b>let </b><font color="Maroon" title="c1">A</font> be    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ;<br/>

<b>assume </b><a NAME="E1:38_1_1"/>
<font color="Maroon" title="c1">A</font> is <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>
 ;<br/>

<b>then reconsider </b><font color="Maroon" title="c2">A'</font> = <font color="Maroon" title="c1">A</font> as  <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>  <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a>  ;<br/>
<a NAME="E3:38_1_1"/>
<font color="Maroon" title="c2">A'</font> is <a href="card_4.html#V1" title="CARD_4:attr.1">countable</a>
 
;<br/>
<b>hence </b><a NAME="E4:38_1_1"/>
<font color="Maroon" title="c1">A</font> is <a href="card_4.html#V1" title="CARD_4:attr.1">countable</a>
 ;<br/>


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