Final answer:
The difference in implicatures between the two utterances is based on the order of events: yelling first and getting fired, or getting fired first and then yelling.
Step-by-step explanation:
The difference in implicatures between the two utterances can be explained by focusing on the order of events. In utterance (a), the speaker first yelled at their boss and as a result, they got fired. This implies that the action of yelling at the boss caused the firing. In utterance (b), the speaker got fired first and then yelled at their boss. Here, the implicature is that the speaker got fired for some other reason, and they later yelled at their boss in response to getting fired.