Sequences And Series

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