An input to the Estimate Activity Resources process is:

The Estimate Activity Resources process involves estimating the team resources and the type and quantities of materials, equipment, and supplies necessary to perform project work. The resource calendar is a critical input because it identifies the working days, shifts, and availability of specific resources. This information directly influences the estimation of the quantity and duration for which a resource is needed, ensuring the estimates are realistic and aligned with resource constraints.

1. Project Management Institute. (2017). A Guide to the Project Management Body of Knowledge (PMBOK® Guide) (6th ed.). Project Management Institute. Section 9.2.1.2, Project Documents, p. 315.

2. Shtub, A. (2016). Project Management: Processes, Methodologies, and Economics (3rd ed.). Pearson. Chapter 5, "The Project and the Organization," discusses resource availability and calendars as fundamental components for planning. (Note: This aligns with the principles taught in university-level project management courses).