Two concentric and coplanar circular coils have radii $\mathrm{a}$ and $\mathrm{b}\left(\gg \mathrm{a}\right)$ as shown in the figure. The resistance of the inner coil is $\mathrm{R}$ and the current in the outer coil is increased from $0$ to $\mathrm{i}$, then the total charge circulating in the inner coil is