During the selection and initiation stage of a major office construction project, sarah was named the project manager. she and her team took the rough high-level information from the project charter and used it as a guideline for preparing detailed project plans. they documented all required deliverables, prepared a detailed schedule and budget, and created other detailed plans that encompassed processes for all of the 10 pmbok® knowledge areas. before starting the work, they obtained final sign-off on their plan documents. what life cycle was being used by sarah and the team?