Let a, a r, a r^2, … … be an infinite G.P. If Σ_n=0^∞ a r^n=57 and Σ_n=0^∞ a^3 r^3 n=9747, then a+18 r is equal to

Let $\displaystyle a, a r, a r^2, \ldots \ldots$ be an infinite G.P. If $\displaystyle \sum_{n=0}^{\infty} a r^n=57$ and $\displaystyle \sum_{n=0}^{\infty} a^3 r^{3 n}=9747$, then $\displaystyle a+18 r$ is equal to