Elapsed time between detection, reporting, and response is the most appropriate metric for evaluating the incident notification process because it measures how quickly and effectively the organization identifies, communicates, and responds to security incidents. The incident notification process is a critical part of the incident response plan that defines the roles and responsibilities, procedures, and channels for reporting and escalating security incidents to the relevant stakeholders. Elapsed time between detection, reporting, and response helps to assess the performance and efficiency of the incident notification process, as well as to identify any bottlenecks or delays that may affect the incident resolution and recovery. Therefore, elapsed time between detection, reporting, and response is the correct answer.
Reference:
https://www.atlassian.com/incident-management/kpis/common-metrics
https://securityscorecard.com/blog/how-to-use-incident-response-metrics/
https://www.cisa.gov/sites/default/files/publications/Incident-Response-Plan-Basics_508c.pdf