wave length of electron beam : 2.14*10^-12 m (2.14 pm)

Camera distance : 0.2 m (200mm)

distances between center point and each point are on picture

Point 1 : 0.374*10^-9 m (0.374 nm)

Point 2 : 0.294*10-9 m (0.297 nm)

Point 3: 0.277*10-9 m (0.277 nm)

i calculated over and over. however it doesn't match

i used this formula

d= Camera constant / distance between center point and point

please let me know what is wrong when i calculated