A dumpy level was set up at the midpoint between two pegs A and B$,50$ m apart and the staff readings at A and B were $1\mathrm{.}22$ and $1\mathrm{.}06.$ With the level set up a A$,$ the readings at A and B were $1\mathrm{.}55$ and $1\mathrm{.}37.$ The collimation error per $100$ m length of sight is

$0\mathrm{.}02$ m inclined upwards

$0\mathrm{.}04$ m inclined downwards

$0\mathrm{.}04$ m inclined upward

none of these.