AWS Certified Solutions Architect Associate Test 10

You have been asked to create VPC for your company. The VPC must support both Internet-facing web applications (ie they need to be publicly accessible) and internal private applications (i.e. they are not publicly accessible and can be accessed only over VPN). The internal private applications must be inside a private subnet. Both the internet-facing and private applications must be able to leverage at least three Availability Zones for high availability. At a minimum, how many subnets must you create within your VPC to achieve this?