This answer states that using who, what, and why is what each user story should include for optimizing a very manual process in its Salesforce org. Who refers to the persona, which is a fictional representation of a typical user or stakeholder who will use or benefit from a feature or a functionality. What refers to the goal, which is what the user or stakeholder wants to accomplish with the feature or functionality. Why refers to the value, which is why the user or stakeholder wants to accomplish the goal, and how they will measure success. Using who, what, and why can help the BA to write effective user stories that capture and prioritize the requirements, and align them with the stakeholder value and expectations. References:
https://trailhead.salesforce.com/en/content/learn/modules/salesforce-business-analyst-quick-look/use-user-stories

Explanation
The business analyst should prioritize US-4007 and US-4009 because they are the most critical work items.
US-4007 is the work item that will allow customers to submit support tickets, and US-4009 is the work item that will allow customer service representatives to view and respond to support tickets. These two work items are essential for the MVP to be functional.
US-4008 is a less critical work item because it will allow customers to track the status of their support tickets.
This work item is important, but it is not essential for the MVP to be functional.
US-4010 is the least critical work item because it will allow customers to rate the quality of customer service.
This work item is important, but it is not essential for the MVP to be functional.
In conclusion, the business analyst should prioritize US-4007 and US-4009 because they are the most critical work items. These two work items are essential for the MVP to be functional.

Explanation
The first step that the business analyst should take to help resolve the issue is to confirm steps to reproduce the issue. Reproducing an issue means following the same steps or actions that caused the issue to occur in order to verify its existence and severity. Reproducing an issue helps to confirm whether it is a real bug or a human error, as well as gather more information about its root cause, impact, frequency, etc. Reproducing an issue also helps to document it clearly and accurately for reporting and resolution purposes. References:
https://trailhead.salesforce.com/content/learn/modules/user-acceptance-testing-video/report-and-resolve-issues