Let a, b, and c be positive integers with a \geq b \geq c such that
\begin{aligned}
a^{2}-b^{2}-c^{2}+a b =2011 \text { and } \\
a^{2}+3 b^{2}+3 c^{2}-3 a b-2 a c-2 b c =-1997
\end{aligned}
What is a ?
Answer Choices
A. 249
B. 250
C. 251
D. 252
E. 253