Exam 1Y0-402 topic 1 question 67 discussion

Scenario: During an assessment of a Citrix Infrastructure, a Citrix Architect finds that there are four active Sites. Each Site has one NetScaler SDX pair and two
StoreFront servers in a server group to allow access for internal and external users. Users have to use different URLs when they access resources from different
Sites. Single-factor authentication is used for both internal and external access. NetScaler appliances are placed in the DMZ with the appropriate firewall ports configured to allow Citrix traffic. Many of the internal users connect using corporate-owned laptops and some external users also connect using personal devices.
The architect needs to provide a design for a multi-tier environment with segregated internal and external traffic on the NetScaler appliance.
How many NetScaler instances and StoreFront servers are required to meet this highly available design?