I'm afraid I do not understand what you are saying here. First, some of the things you are listing as "variables" are not variables but constants: you pay the "booth rental" and "gas", etc. only once for each event. Also you say that "order forms" and "receipts" are $10. Surely that is not the cost of each order form or receipt! You need the cost of each one. Also, do you use both an "order form" and a receipt for each sale? And you can use some of those things, such as the "decorations" at more than one place can't you?