Exam 70-705 topic 3 question 14 discussion

A customer wants to buy 300 Microsoft Office 365 Enterprise E1 User Subscription Licenses (USLs) and 300 Office 365 Enterprise E3 USLs for services. The licenses will be managed by an experienced IT team.
The customer expects to add licenses for additional users during the next two to four years. The customer wants a guarantee that the purchase price of the licenses will remain the same as the current prices throughout the four-year period.
According to the customer's internal purchasing process, payment for the services must be upfront and on a quarterly or annual basis.