Simplify the Exponential Expression $$\left( 9 x ^ { 16 } y ^ { - 18 } \right) ^ { 5 / 2 }$$

Multiple Choice

Simplify the exponential expression. Write any negative exponents as positive exponents. Assume all variables represent positive real numbers.
- $$\left( 9 x ^ { 16 } y ^ { - 18 } \right) ^ { 5 / 2 }$$

A) $\frac { 243 x ^ { 40 } } { y ^ { 45 } }$
B) $243 x ^ { 40 } y ^ { 45 }$
C) $\frac { 9 x ^ { 40 } } { y ^ { 45 } }$
D) $\frac { 243 } { \mathrm { x } ^ { 40 } \mathrm { y } ^ { 45 } }$