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