The length of a potentiometer wire is $1200 \mathrm{c}\mathrm{m}$ and it carries a current of $60 \mathrm{m}\mathrm{A}$ For a cell of $\mathrm{e}\mathrm{m}\mathrm{f} 5 \mathrm{V}$ and internal resistance of $20 \mathrm{\Omega }$ the null point on it is found to be at $1000 \mathrm{c}\mathrm{m}$ The resistance of whole wire is: