The cloud computing model that would best suit the organization's requirements of low maintenance needs is Software as a Service (SaaS).
In the SaaS model, the organization can access and use the collaboration software as a service over the internet without having to worry about managing the underlying infrastructure or performing software maintenance tasks. The responsibility for maintaining the software, including updates, security patches, and backups, lies with the SaaS provider.
By choosing SaaS, the organization can offload the burden of software maintenance to the provider, allowing their limited IT staff to focus on other critical tasks. SaaS provides a complete software solution that is ready to use, eliminating the need for the organization to manage the underlying hardware, operating systems, or middleware.
Option b) Software as a Service (SaaS) is the best fit for the organization's requirements.