Since comets are in orbit around the sun, just like planets, their motion
in the night sky will be very similar to planets, namely they will move
very slowly with respect to the background stars. So two hours later the
comet will be seen in the southwest due to the general east-west motion of
objects in the sky (diurnal motion) and it will be close to star b (i.e. it
will not have shifted noticably in position relative to the background stars.