A circular current carrying coil has a radius $R$. The distance from the centre of the coil on the axis where the magnetic induction will be $\frac{1}{8}$ th of its value at the centre of the coil, is:
(a) $R \sqrt{3}$
(b) $\frac{R}{\sqrt{3}}$
(c) $\frac{2 R}{\sqrt{3}}$
(d) $(2 \sqrt{3}) R$