Im guessing you meant 12.25.11
It would be more likely that guy B is the father.
First Day of Last Menstrual Period: December 25, 2011
Probable Date of Ovulation: January 8, 2012
Possible Dates of Conception: January 4 to January 12, 2012
Due Date: September 30, 2012 (40 weeks)
Best of luck to you and your baby.