In \triangle A B C we have A B=7, A C=8, and B C=9. Point D is on the circumscribed circle of the triangle so that \overline{A D} bisects \angle B A C. What is the value of A D / C D ?
Answer Choices
A. \dfrac{9}{8}
B. \dfrac{5}{3}
C. 2
D. \dfrac{17}{7}
E. \dfrac{5}{2}