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<b>let </b><font color="Maroon">c<sub>3</sub></font> be    <a href="subset_1.html#M2">Element</a> of <font color="Maroon">c<sub>2</sub></font>;<br/>

<b>thus </b><a NAME="E1:96_1_1"/>
<font color="Maroon">c<sub>3</sub></font> is    <a href="trees_1.html#M1">Element</a> of <font color="Maroon">c<sub>1</sub></font>
 ;<br/>


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