In a potentiometer experiment, when two cells of emfs \( E_1 \) and \( E_2 \) (\( E_2>E_1 \)) are connected in series, the balancing length is 160 cm. If one of the cells is reversed, the balancing length decreases by 75%. If \( E_1 = 1.2 \, V \), then \( E_2 \) is