Hello Ghanshyam, and welcome to the forums.
First - nicely done with the Google rankings. Most people I talk to have ranking problems in the other direction: good on Bing and challenges on Google.
I wish I could give you a concise formula, but I don't have that magic secret. About all I can say is that ranking on Bing seems to be more like ranking on Google was a couple years ago.
There may be something about Facebook folded into the mix these days - at least people are speculating about that - but again I've really got nothing definitive to say. Bing is becoming more complex and simple formulas are hard to come by.