Final answer:
The team is in the Norming stage, as indicated by the resolution of initial conflicts, the establishment of a team leader, and clearer understanding of team roles.
Step-by-step explanation:
At the end of the scenario described, the team is in the Norming stage of team formation. This stage is characterized by the resolution of conflicts, the emergence of strong team leadership, and the establishment of clear roles and responsibilities within the group. The team members have gone through a productive argument that led to self-awareness and mutual feedback, which is a key component of the Norming phase. They have united under Jacquelin's even-tempered leadership and have started working earnestly on the problem. This indicates that the team has moved past the Storming stage, where conflicts and friction are prevalent, and into a stage where cohesion begins to develop.
The team is at the Norming stage of the team formation process. This is indicated by the appointment of Jacquelin as the unofficial leader and the understanding of the members' roles on the team.