In triangle A B C, side \overline{A C} and the perpendicular bisector of \overline{B C} meet in point D, and \overline{B D} bisects \angle A B C. If A D=9 and D C=7, what is the area of triangle A B D ?
Answer Choices
A. 14
B. 21
C. 28
D. 14 \sqrt{5}
E. 28 \sqrt{5}