Let $a, b$ and $c$ be the $7^{\text{th}}, 11^{\text{th}}$ and $13^{\text{th}}$ terms respectively of a non-constant A.P. If these are also the three consecutive terms of a G.P., then $\frac{a}{c}$ is equal to:\\
(1) 2\\
(2) $\frac{7}{13}$\\
(3) $\frac{1}{2}$\\
(4) 4