The difference of speed of light in the two media A and B (v_A $-$ v_B) is 2.6 $\times$ 10⁷ m/s. If the refractive index of medium B is 1.47, then the ratio of refractive index of medium B to medium A is : (Given : speed of light in vacuum c = 3 $\times$ 10⁸ ms^$-$1)