This project is a formal proposal. The document should propose a course of action that would result in greater understanding of the problem. That is, rather than propose solutions to the problem, you will propose ongoing investigation of the problem to better facilitate the development of a solution.
Include the following elements in your Proposal.

Letter/Memo of Transmittal. A cover letter or cover memo to an appropriate audience that introduces the problem, the solutions, and the final recommendation.
Summary. A detailed but brief summary of the key points in the proposal including the final recommendation.

Table of Contents. This should be self-explanatory. You should include the major sections of the proposal.
Table of Figures. This should be self-explanatory.
Introduction. Introduce the proposal topic and structure. (Begin normal document pagination here, identifying the first page as page 1.)
Problem History. Provide an explanation of the problem, including evidence that there is a problem, the history of the problem, previous attempts to address it, potential consequences of inaction, and any other information that seems pertinent.
Proposed Investigation Process. Discuss in detail the investigation process that you argue represents the most logical or effective approach to studying the problem, given your understanding of the problem, the available resources, and any other factors that might influence a solution to it. Explain clearly and directly what steps and methods you propose for your investigation, and how you think it will facilitate greater understanding of the problem.
Project Timeline. Provide a project timeline. Provide whatever detail is relevant to your proposed investigation. Discuss milestones, and when each will be reached.
Proposal Budget. Identify all resources (e.g., funds, expertise, time, facilities) required to complete the project you propose. This should include a summary table of expenses that provides accurate market value for all resources requested or required.
Conclusion. Briefly recap your proposed investigation, stating directly and clearly why you feel your plan represents the best possible course of action for studying the problem at this time.