What type of requirement is illustrated by the following: 'The first page of report Y will be displayed for the user within 5 seconds of the request'?

The statement 'The first page of report Y will be displayed for the user within 5 seconds of the request' describes a characteristic related to the performance of a system, specifically the response time that a user can expect when accessing a report. This characteristic falls under the category of non-functional requirements, which address how a system performs its functions rather than what functions it performs.

Non-functional requirements encompass various aspects such as performance, security, usability, and reliability. In this case, the requirement specifies a quantitative measure related to speed which directly impacts user experience and system performance. Non-functional requirements are essential because they determine the quality of the system’s operation and overall user satisfaction.

While the other choices such as usability or reporting might also touch on aspects of user experience or the nature of the output, they do not capture the specific focus on performance and timing represented in the given statement. Thus, identifying the requirement as non-functional accurately reflects its emphasis on system efficiency and responsiveness.