Answer : a. Community
Allows a system to be accessible by a group of organizations. It can be shared between several organizations. It may be managed by organizations or by the third party.
This should be chosen by Ryan, since this computing model is cost effective and best to share among companies and organizations.
Other options explained:
-Software model is accessible via a browser and multiple users can use it.
-Infrastructure model is based on providing services of computer architecture in a virtual environment