[A4] Trailer Hitch for Thule T2 Rack

[gsackerson at comcast.net]

Hi all,
  I have a 2005 A4 (2.0T Quattro,) and I've been eyeing the bicycle rack that the Thule company makes, which connects to a trailer hitch. My question is this: Can a trailer hitch be used on an A4 and if so, have any of you done so? I went to the Thule web site to try and find out if this model T2 rack could be used with my make and model car, but it started asking questions like:

(1) Is the hitch a 2" or 1 1/4" hitch?
(2) What class is my hitch - Class 2, 3 or 4?

I realize the answers to the above would depend on what I was towing - whether it was a motorcycle trailer, a boat or an trailer. But, I wondered if any of you have mounted hitches, and if so, whether you know the answers to any of the above as well as an approximate cost of a hitch mount?

Glenn