Certinia PSA utilizes Work Calendars to define the standard working hours and days for resources, which is fundamental for calculating capacity and utilization. The scenario explicitly outlines two distinct groups for resource planning: full-time employees and part-time employees, with the latter group being standardized to a 20-hour week for planning purposes. Therefore, the most appropriate and efficient setup is to create two Work Calendars: one to represent the standard full-time schedule and a second one to represent the standardized 20-hour per week part-time schedule. This directly aligns with the system's design and the stated management requirements.

A. Creating a calendar for each unique part-time contract is administratively burdensome and contradicts the management directive to use a standardized 20-hour estimate for planning.

C. The scenario does not provide any information that would necessitate a third, "generic flexible" work calendar. The two defined groups are sufficient to meet the requirements.

1. Certinia PSA Administration Guide, Section: "Work Calendars". This section details that Work Calendars are used to model the different working patterns within an organization, such as for full-time and part-time employees, to accurately calculate resource capacity. The guide recommends creating distinct calendars for such groups.

2. Certinia Help Portal, Article: "Setting Up Work Calendars". The documentation states, "You can create multiple work calendars to reflect the different working patterns in your organization... For example, you might have different calendars for full-time and part-time employees, or for resources in different countries." This directly supports creating one calendar for the full-time group and another for the part-time group.