Simplify the Expression $\left( 8 a ^ { 5 } \right) \cdot \left( 2 a ^ { 8 } \right)$

Multiple Choice

Simplify the expression. Assume all variables represent nonzero real numbers.
- $\left( 8 a ^ { 5 } \right) \cdot \left( 2 a ^ { 8 } \right)$

A) $16 a ^{40}$
B) $16 a ^ { 13 }$
C) $10 ^ { 13 }$
D) $10^{40}$