But it does not say if  it better to pay a fixed fee to the company, or one that varies depending on the number of students attending? But my model does have the fee for a standard fixed fee but also calculates the cost using the options and in my opinion a fixed fee is worse as it means that you do not charge more or less if the option is cheaper or more expensive so for both the company so the fixed fee is what it would have cost if you picked the most expensive options otherwise the company may actually lose money. Furthermore the customer it is worse to have fixed and you can somewhat see this from my model but it has not been explicitly answered.

It also does not answer if the number of students attending increases as I have assumed that  that we would not provide the staffing and it would be teachers doing the staffing and therefore would not be need to be included in my model. 

My Prom model can calculate all costs, including the activities and catering and ticket prices. You are able to change the entertainment catering amount of people and the cost will automatically work it out, model also answers many 'what-if' questions such as: what if the ticket price become too high or what if the number of students attending increased.

Nearly all input done