A point object is placed on principal axis of a concave mirror ( of focal length 15 cm) at a distance $\mathrm{u} = 61 \mathrm{cm}$ from pole. A slab of thickness $\mathrm{t} = 3 \mathrm{cm}$ and refractive index $\mathrm{\mu }= 1.5$  is placed with two sides perpendicular to principal axis, such that its nearest face is x₀ cm from pole. The final image of object is to be considered after refraction by slab, reflection by mirror and final refraction by slab.