AutoCAD Inventor :: Multiple Extrusion Depths On Same Part

Inventor 2014.  I have watched everything I can find and read many entries on related messages.

I create a part by creating rectangle on the XY of 90mm centered on 0,0.  I add fillets on 3mm on all four corners.  I then add two circles centered on 0,0 of diameters 45 mm and 41mm.  What I would like to do is extrude the area between 41 mm and 45 mm circles to 10 mm and the rest of the rectangle outside of the circle 45 mm circle to 6 mm.  The center of the part from center to the 41 mm circle is void or open. 

I have read two solutions that use a "share sketch" function, that I can't find by right-clicking as indicated in the write-up.