Sad Fate

11)After the murder above... a) who was then proclaimed Emperor ? He associated his son with him, as a joint ruler - b) what was the name of this son? There were many frontier problems, and the Emperor himself left Rome to campaign in the East - however after a few years of successful campaigning, his army was surrounded and he, the Roman Emperor, was taken prisoner - c) in what year did this take place?..... d)What was the name of the ruler who held him prisoner? (give name and number - eg Mark III)