What type of document typically includes a written plan identifying a problem and its constraints?

The Design Brief is the correct answer because it serves as a foundational document in the engineering and design process. It outlines the objectives and scope of a project, specifically detailing the problem that needs addressing and the constraints that must be considered throughout the design process. This document helps guide the development of creative solutions by clearly defining what is needed and any limitations, such as budget constraints, timeline, and materials.

In contrast, an Engineering Notebook is primarily used to document the processes, thoughts, and experiments during the design and engineering stages but does not serve as a planning document in the same way. A Design Statement, while related, tends to focus on summarizing the goals and approach rather than laying out a structured plan with constraints. A Prototype represents a tangible manifestation of ideas and decisions made during the design process, which occurs after the planning as described in the Design Brief.