Answer:
c. Install a proxy server
Step-by-step explanation:
In computing a proxy server is implemented as a middle 'man' between the user and the internet. It will hence behave as a gateway that will seperate users from the websites that they browse. The major importance of a proxy server is enforcing security, however it can also act as a web filter allowing organizations to restrict access to certain websites. So when an organization or a school wishes to prevent access to certain sites a proxy server will be implemented, in the question scenario this web filter feature can be used to save cost associated with visiting sites not relevant to the organization's objectives