actionscript-3 - How to use "this" in Flash Builder 4.5

Question

I'm trying to learn Flash builder 4.5, and now I'm stuck with this question.

I got this code:

<fx:Script>
    <![CDATA[
        public function showList():void
        {
            tier2.x=(this.x+this.width);
            tier2.y=(this.y+this.height);
            tier2.visible=true;
        }
    ]]>
</fx:Script>

// on mouseover I'm calling function showList()
<mx:LinkButton x="10" y="20" width="143"
               label="Class 1" id="t_id1"
               mouseOver="showList()"
               color="#FFFFFF" fontFamily="Arial" fontSize="16" fontWeight="bold"/>

<s:List id="tier2" visible="false" width="111" borderColor="#FEFEFE"
        borderVisible="true" color="#FAF3F3" contentBackgroundAlpha="0.5"
        contentBackgroundColor="#5D5E5E">
</s:List>

In function showList() I'm trying to move the list to the linkbutton on mouseover.

How can I get the linkbutton's x and y position?