Find the Coefficient a of the Term in the Expansion $\left( x ^ { 2 } + 8 \right) ^ { 12 } a x ^ { 8 }$

Multiple Choice

Find the coefficient a of the term in the expansion of the binomial.​ Binomial Terms
$\left( x ^ { 2 } + 8 \right) ^ { 12 } a x ^ { 8 }$ ​

A) 8,304,721,920
B) 8,304,721,921
C) 8,304,721,923
D) 8,304,721,918
E) 8,304,721,919