A PM is reviewing bids from vendors and has a question. Which of the following documents should the PM use to obtain a response?

A project schedule is an internal planning artifact that tracks tasks and timelines - it has no role in vendor communication or procurement.

A Request for Proposal (RFP) is the procurement document used to formally invite vendors to submit detailed proposals in response to defined project requirements. It establishes the criteria, scope, and terms against which vendor bids are evaluated, making it the correct instrument when the PM needs vendors to provide formal responses.

A quotation is a document generated by the vendor providing pricing information - it is a vendor's response, not a document the PM uses to solicit information.

An RFI (Request for Information) is used to gather general market information before procurement begins, and is not the appropriate tool for formally soliciting bids or proposals from vendors already in the evaluation process.