
Explanation:

Web tier: Use 2 Standard tier VMs in a new availability set, load balanced with Azure Load
Balancer.
The web tier must support high volumes of incoming Internet traffic during peak times throughout the year.
Services: Use 2 Standard Tier VM in a new availability set.
Data: Use 2 Standard tier VMs contained within the services tier availability set.
Processing: Use 2 Dv2-series Vms in a new scale set.
The processing tier must support high volume CPU loads at peak times throughout the year.
Dv2-series, a follow-on to the original D-series, features a more powerful CPU. The Dv2- series CPU is about 35% faster than the D-series CPU.
Automatic scaling of virtual machines in a scale set is the creation or deletion of machines in the set as needed to match performance requirements. As the volume of work grows, an application may require additional resources to enable it to effectively perform tasks.
References:
https://docs.microsoft.com/en-us/azure/virtual-machines/virtual-machines-windows-sizes
https://docs.microsoft.com/en-us/azure/virtual-machine-scale-sets/virtual-machine-scale-sets-autoscale-overview