JEE Advanced Model Paper 11 with solutions for online practice

A quarter portion of a thin equi-convex lens with focal length 30 cm has been removed by cutting it perpendicular to the principal axis as shown. A small object is placed on principal axis at a large distance from lens and is moving towards the lens.At an instant, it is observed that the relative velocity between the two distinct images (corresponding to paraxial rays) is zero. The distance of object at this instant is 5 k (K ≠ 0) centimeters what is ‘k’?