Approver License

Hi All, I'd like to know how the license model for AME looks like. I have the following scenario in mind on which I do not find any dedicated information while searching through the license information pages. User A is a Purchaser and has Purchasing license and respective responsibilities.User B who is the supervisor of User A has no Purchasing license and no active responsibilities in the system.User A creates a PO for which he hasn't enough limit to approve. The PO is being assigned to User B.AME generates an approval Mail for User B. User B approves via Mail.