According to the PMBOKGuide, a project manager should be able to plan and manage the project schedule, taking into account the availability and capacity of resources, as well as the project constraints and assumptions. When a project involves multiple international locations, the project manager should also consider the cultural and environmental factors that may affect the project performance, such as holidays, working hours, communication preferences, and legal requirements. In this scenario, the project manager realized that some of the key activities were scheduled over the holiday periods in the overseas offices, which caused delays in the project. The project manager should update the schedule to reflect the holidays and share the workload among offices to mitigate schedule slippage. This option demonstrates the project manager's ability to adjust the schedule based on the actual resource availability and to balance the resource allocation across different locations. Updating the schedule and sharing the workload may also help to maintain the team's morale and productivity, as well as the stakeholder's satisfaction. Hiring additional personnel on a temporary basis, requesting that the offices in overseas locations work overtime, or notifying the project sponsor of the delayed completion are not effective or appropriate actions to take in this situation. These options may incur additional costs, risks, or conflicts, and may not address the root cause of the problem. They may also indicate a lack of planning, communication, or collaboration skills on the part of the project manager. References: PMBOKGuide, 6th edition, pages 191-192, 267-268, 349-350.