This is a ‘paper’ assignment and should, therefore be in APA format—title page, abstract, paper, and Appendices. Appendix 1 should contain any references. Figures require figure numbers and captions. Figure captions should describe what is significant about the figure. Don’t say “Figure 1: A plot of the cost.” That will be obvious from the figure. If you use a figure, there should be a reason for it. The abstract should be advertising for your paper (it is not a summary) and showcase the key results. (So that the reader wants to read the paper and discover how you got those fascinating results.) This does not need to be a long paper—a couple of pages is quite sufficient. The main goal is to show that you can manipulate Excel and present PM data in a clear and appropriate context. You may make up any scenario for the data that you like. Have fun. Present the data in any context you can make a case for.
Since you don’t know any of the details of the project except for the planned and actual costs over time, you need to examine the data and describe what it shows happened in the project throughout its conduct. Then describe what you found out in the paper you wrote. Be sure to include the chart that you’ve developed as an appendix, or you may include it in the MS Word document itself at the appropriate point. Be sure to label everything properly so it’s easily understood.