In the given figure, the image of object AB observed by observer is

Object shiftnessx=t1−1μ=151−23=5cmThe image of AB is A1B1 due to refraction through slab, which is shifted 5 cm from AB. The size of A1B1 is same as that of AB.A1B1 Behaves as object for the lens.For convex lens, A1B1 behaves as object.For lens, u=−60cm,f=20cm  1v−1u=1f   or  1v+160=120  Or   1v=120−160=3−160 ∴v=+30 cm ∵A2B2A1B1=vuOr    A2B2=vuA1B1=30−602cm=−1 cmThus, final image A2B2 is real, inverted, 1 cm in length and is 30 cm from the lens.