Exercise 1 solution

For W=4000, H=3000 the thirds are x = 1333.3 and 2666.7, y = 1000 and 2000.
Power points: (1333, 1000), (1333, 2000), (2667, 1000), (2667, 2000).
Subject at (1400, 900): nearest is (1333, 1000). Distance = hypot(66.7, 100) = about 120 px, roughly 2.4% of the 5000 px diagonal.