The length of a potentiometer wire is 1200 cm and it carries a current of 60 mA. For a cell of emf 5V and internal resistance of 20 Ω, the null point on it is found to be a 1000cm. The resistance of whole wire is :
(1) 120 Ω
(2) 60 Ω
(3) 80 Ω
(4) 100 Ω