In a corporate environment, an organization is implementing a new Identity and Access Management (IAM) system to enhance security and streamline user access. The system will utilize role-based access control (RBAC) to assign permissions based on user roles. If the organization has 5 distinct roles, each with a unique set of permissions, and each role can be assigned to multiple users, how many unique user-role combinations can be created if there are 20 users in total? Additionally, if the organization decides to implement a policy that restricts any user from having more than one role at a time, what is the maximum number of users that can be assigned to the role with the highest permissions if that role can accommodate up to 10 users?