Simplify the Expression $\left( \frac { 3 a ^ { 2 } b } { a ^ { - 5 } b ^ { 4 } } \right) ^ { 3 }$

Essay

Simplify the expression. Write the answer using positive exponents. $\left( \frac { 3 a ^ { 2 } b } { a ^ { - 5 } b ^ { 4 } } \right) ^ { 3 }$