Problem 5 – Hint 5

To sum up all the hints: first, construct a focal plane using the intersection points of the images of two parallel lines (hints 3,4). Second, find the intersection points of the images of two pair of mutually perpendicular lines. Third, construct two circles through these four points. Reasoning behind the second and third steps can be found in the solution of the  Problem 4 of Physics Cup – 2017.