Task:  Healthy Beat Ltd. is a medical device firm to develop and manufacture heart-rate monitors. Recently the top management team has decided to implement a MES(Manufacturing Execution System) software solution to vastly enhance its production line efficiency and reduce production leadtime.  The supplier of this MES software solution is called NAME_1. 
Issue 4: In the middle of the project, you receive an additional requirements from top management asking your project team to integrate the MES software system with WMS (Warehouse Management System).  It will increase the cost to NAME_1 by approximately 100K and there is no additional budget for this project scope creep. Additionally, it will also increase the project duration by 1 months. You are required by the senior management to negotiate with NAME_1 to accept this additional work with no charge. In the negotiation, NAME_1 says that they can stay with the current cost, but need to increase the maintenance hourly rate and tell you in private that this is the future cost and will not appear in the current contract and invoice.
在这种情况下，涉及哪些重要的利益相关者？