Two coils of radii $R_1$ and $R_2$ are concentric and coplanar. The mutual induction between coils is proportional to  ${R^2}_1/R_2.$ The current flows in larger coil. Find the correct option : 

Let  $R_1<R_2$
Current flows in large coil of radius  $R_2$
Magnetic field at centre   $=\frac{{\mu }_{0}i}{2R_2}$
Flux linked with smaller coil $=\pi {R^2}_{1}B=\pi {R^2}_1\frac{{\mu }_{0}i}{2R_2}$
$\varphi =Mi$
$M=\varphi /i=\left(\frac{{\mu }_0\pi }{2}\right)\frac{{R^2}_1}{R_2}$
$M\propto \frac{{R^2}_1}{R_2}$
Hence, $R_1<R_2$                   otherwise,  $R_1>R_2$