Based on the backlog metrics in the chart, what can explain the jump in points at the end of iteration 4?

A project's product owner asks the scrum master to facilitate the estimation activity. The scrum master then meets with the team and the product owner to clarify the user stories. Following the meeting, the team assembles and provides individual user-story estimates. What technique did the team use?

An event management team is following an agile approach to prepare for an upcoming conference. The regional sales manager, from where the conference is to be held, contacts the team with a number of questions about the company's booth.
What should the team do?

Which is NOT a principle of Lean?

During backlog refinement meeting, the new developer on the team asks the product owner to discuss a new performance threshold requirement and how it impacts the stories in the backlog.
What should the team do?