Get absolute coordinates a child shape

Sorry for my English.

A PowerPoint slide contains a group shape (grpSp) with following coordinates:

<a:offy="2058985"x="244799"/><a:extcy="2264343"cx="7118946"/><a:chOffy="2058986"x="244799"/><a:chExtcy="1942187"cx="5727249"/>

This group shape contains a child shape (sp) with following coordinates:

<a:offy="3084512"x="244799"/><a:extcy="916661"cx="1710237"/>

After ungrouping the child shape contains follow coordinates:

<a:offy="2058986"x="244799"/><a:extcy="1064224"cx="2545581"/>

As you can see coordinates are changed - converting to absolute coordinate on the slide.

I cannot programmatically to make the formula to get these absolutely coordinates. Which formula should I use to convert a child shape's coordinates to absolute as shown in the example (cx="1710237" => "2545581")?