In the given potentiometer circuit arrangement, the balancing length AC is measured to be 250 cm. When the galvanometer connection is shifted from…

In the given potentiometer circuit arrangement, the balancing length AC is measured to be $\displaystyle 250$ cm. When the galvanometer connection is shifted from point ($\displaystyle 1$) to point ($\displaystyle 2$) in the given diagram, the balancing length becomes $\displaystyle 400$ cm . The ratio of the emf of two cells, $\displaystyle \frac{\varepsilon_1}{\varepsilon_2}$ is :