Since this is an interviewer-led case, the interviewer should guide the interviewee through the interview.
The case is split into two parts.
The first part is more qualitative. The open-ended questions should prompt the interviewee to think about the problem and its solution.
The second part is more quantitative in nature. In order to solve the questions, the interviewee should perform calculations. The questions in the big boxes should be read out to the candidate.
There is a new napkin dispensing technology on the market. Since you think it could save the client money, you decide to investigate.