$\begin{aligned} & \mathrm{i}=\mathrm{K} \theta \\ & \frac{2}{\mathrm{G}+R}=K \theta \\ & \Rightarrow \frac{1}{\theta}=\frac{(\mathrm{G}+\mathrm{R}) \mathrm{K}}{2}=\mathrm{R}\left(\frac{\mathrm{K}}{2}\right)+\frac{\mathrm{KG}}{2} \\ & \text { Slope }=\frac{\mathrm{K}}{2}=\frac{1}{4} \Rightarrow \mathrm{~K}=0.5=5 \times 10^{-1} \mathrm{~A}\end{aligned}$