Explanation:
Box 1: 2
One management group for East, and one for West.
When creating a blueprint definition, you'll define where the blueprint is saved. Blueprints can be saved to a management group or subscription that you have Contributor access to. If the location is a management group, the blueprint is available to assign to any child subscription of that management group.
Box 2: 1
One definition as the you plan to deploy a custom application to each subscription.
With Azure Blueprints, the relationship between the blueprint definition (what should be deployed) and the blueprint assignment (what was deployed) is preserved.
Box 3: 4
One assignment for each subscription.
Reference:
https://docs.microsoft.com/en-us/azure/governance/blueprints/overview