Exam 1Y0-403 topic 1 question 16 discussion

Scenario: Engineers at a new company developed their product and infrastructure in Microsoft Azure. The engineers have reached out to a Citrix Architect to help design an Azure infrastructure to support publishing applications using the Citrix Virtual Apps and Desktops service. Costs need to be kept to a minimum.
Which Azure virtual machine (VM) series provides the lowest cost per user while also providing good performance?