A screw gauge has some zero error but its value is unknown. We have two identical rods. When the first rod is inserted in the screw, the state of the instrument is shown by diagram (\(I\)). When both the rods are inserted together in series then the state is shown by the diagram (\(II\)). What is the zero error of the instrument?
Note : 1 msd = 100 csd = 1 mm