A coin lies at the bottom of a tank filled with two immissible liquid. Liquid 1 on top is $20\;cm$ layer thick of refractive index $\mu_1 =1.33$ and liquid 2 is $40\;cm$ thick with refractive index $\mu_2=1.46$. At what depth below the surface the coin appear?

Question

$(a)\;60\;cm \\ (b)\;48\;cm \\ (c)\;50\;cm \\ (d)\;42\;cm$