With tight planning, the most efficient and prudent course of action is to issue a Request for Proposal (RFP) to a shortlist of pre-approved vendors. This approach balances speed with due diligence. The pre-approval process ensures that the vendors have already been vetted for financial stability, technical capability, and reliability. Conducting an RFP among this select group fosters competition, leading to better value and a more robust solution, while significantly shortening the overall procurement timeline compared to starting an open market search with a Request for Information (RFI).

A. A Request for Information (RFI) is used for market research and would add significant time, which contradicts the "tight planning" constraint.

C. Postponing the project is a risk mitigation strategy of last resort and is not a proactive step in the vendor selection process.

D. Appointing a vendor without a competitive process like an RFP introduces significant risks related to cost, quality, and lack of transparency.

1. University of California. (2020). Procurement: A Guide to Strategic Sourcing. Section on "Supplier Selection," pp. 15-17. This guide outlines the use of pre-qualified supplier lists to streamline the RFP process for time-sensitive projects.

2. Massachusetts Institute of Technology (MIT). (n.d.). Procurement and Payment Methods. MIT's procurement guide details the appropriate use of RFPs and preferred/pre-qualified vendors to ensure efficiency and compliance.

3. National Institute of Governmental Purchasing (NIGP). (2010). The Request for Proposals (RFP) Practice. This official guide discusses how using a pre-qualified list of bidders (Section 2.4) is a standard practice to increase the efficiency of the RFP process.