In a series $\mathrm{LR}$ circuit, power of $400 \mathrm{W}$ is dissipated from a source of $250 \mathrm{V}, 50 \mathrm{Hz}$. The power factor of the circuit is $0.8$. In order to bring the power factor to unity, a capacitor of value $\mathrm{C}$ is added in series to the $\mathrm{L}$ and $\mathrm{R}$. Taking the value of $\mathrm{C}$ as $\left(\frac{\mathrm{n}}{3\mathrm{\pi }}\right) \mathrm{\mu F}$, then value of $\mathrm{n}$ is