I'm sure he's not the only one who knows how to figure that out.Forgive me but you sound like you've never taken on anything like this before in your life.
Further, how can you expect to get accurate advice when you offered basically no facts about the event,the most important being the number of people attending?
Besides the late great Pete's posts, as our own wise and wonderful Mimi
has suggested, there is a wealth of posts on this site about that very subject. A simple search in the archives for catering pricing will return many useful discussions on it.
Why not ask them a few questions?
How many people are going to be at the party?
Are you going to have it completed before you get there?
Are you going to have to set anything up? Or are you just bringing your product?
I wouldn't worry about how much you charge, worry about how tasty your product is, and how well its organized.
if this is your first time doing something like this, go in there with your product complete, and be confident everyone is going to enjoy your food.
The quality of your product and the value it provides for your customer is what will decide what its worth for them to pay.
They'll ask you how much you want for your services, and I'd suggest basing your profit off the perceived value. If they didn't really eat it and its not that great, i'd ask for the price you paid for the food, and work on your recipes.
If they loved it and its all gone, charge 2x - 4x what you paid, because you won't seem greedy for doing so, especially if they loved it, it'll be worth it for them to accommodate your services.
I hope i've helped a little bit. Please feel free to ask questions. I currently run a small catering business.