Current Electricity

A potentiometer wire of length $4\ \text{m}$ and resistance $5\ \Omega$ is connected in series with a resistance of $992\ \Omega$ and a cell of e.m.f. $4\ \text{V}$ with internal resistance $3\ \Omega$. The length of $0.75\ \text{m}$ on potentiometer wire balances the e.m.f. of