For two positive numbers $a , b$, $$\left\{ \begin{array} { l }
ab = 27 \\
\log _ { 3 } \frac { b } { a } = 5
\end{array} \right.$$ When these conditions hold, find the value of $4 \log _ { 3 } a + 9 \log _ { 3 } b$. [3 points]
For two positive numbers $a , b$,
$$\left\{ \begin{array} { l }
ab = 27 \\
\log _ { 3 } \frac { b } { a } = 5
\end{array} \right.$$
When these conditions hold, find the value of $4 \log _ { 3 } a + 9 \log _ { 3 } b$. [3 points]