A homogeneous column of water with refractive index a$$\mu_w=4/3$$ and height 8.0 $$\mathrm{cm}$$ fills the space above a 9.0 $$\mathrm{cm}$$ thick glass slab with refractive index a$$\mu_g=3/2$$. Observers A and B are in air just outside the top and the bottom whereas the observers C and D are inside just below the top and above the bottom. The total thickness of glass plus water
observed by these observers are