The presentation will be on the case study. However, I know some people who had 10 minutes to present it (as asked) while the partner was listening and I know others who talked for 10 seconds and were immediately asked questions to clarify their assumptions and what they wrote!So: think quickly and on your feet! You must be ready to prove what you are saying. Keep in mind some key elements and numbers (roughly). It will show you did understand the case study thoroughly. You may, however, make mistakes or deliver inaccurate comments, especially if you're not from a business background. As long as you try your best to answer correctly...
