1) Who determines the benefits of a project?

2) What benefits are determined for each component of the project deliverables or the deliverables themselves? For example, for a new generation airplane, many changes will be made to the aircraft. Does the organization look at and approve the benefits of the newly designed wings, the engines, the landing gear, or the new avionics built into the aircraft, or does the organization only look at the benefits of the new aircraft as a unit?

3) why should an organization plan out the expected benefits of a project before it is built?