Current Electricity

A potentiometer wire of length \(300 \mathrm{~cm}\) is connected in series with a resistance 780 \(\Omega\) and a standard cell of emf \(4 \mathrm{V}\). A constant current flows through potentiometer wire. The length of the null point for cell of emf \(20\, \mathrm{mV}\) is found to be \(60 \mathrm{~cm}\). The resistance of the potentiometer wire is ____________ \(\Omega\).