CAT 2024 Logarithms — Previous Year Question

If $a, b$ and $c$ are positive real numbers such that $a>10 \geq b \geq c$ and $\frac{\log _8(a+b)}{\log _2 c}+\frac{\log _{27}(a-b)}{\log _3 c}=\frac{2}{3}$ , then the greatest possible integer value of $a$ is