I tried searching for it on bing :). The only thing that even had an estimate was http://searchengineland.com/microsoft-search-ad-revenue-esti...

Their guess was between 900 million and 1.8 billion, or large but they haven't a clue. 47% should be in the ballpark of a few hundred million.

I think they're on track to do $2 bil this year for some context.