Classless Inter-Domain Routing and Subnetting

After learning about classful addressing, we know how the IP address blocks have been organized into different ranges within classes, each with a different number of IP addresses. Is it scalable and sustainable to assign IP addresses using classful addressing? Assume we require 400 IP addresses for our office network; which class of IP range should we choose to meet our needs?

We can’t use class C because it only allows for 256 IP addresses in a network; our other options are class A ...