You have a Microsoft Dynamics CRM 2016 deployment and you have not purchased any additional subscriptions besides your 15 user licenses.
Your organization plans to test a new Independent Software Vendor (ISV) software. You currently have 1.3 GB of production data.
You are instructed to use full copies of the data for testing purposes and to create three more sandbox instances to replicate the production environment. Each of the three instances will be used to test one ISV solution. You have 10 users from the production environment who will test all three test environments.
You need to determine which additional subscriptions you need. What is the minimum requirement for additional subscriptions?