Your final task is to analyse and explain how your final design is "fit for purpose."
"Fit for purpose" means that the design of a product adequately meets its intended use, meets the requirements, and fulfils the expectations of its users or stakeholders.
The best ways I suggest to do this are:
List your final requirements and specifications, then explain and justify why you have included these. See the table in your workbook for an example.
Label your final design, showing how and where your design meets the requirements and specifications