I need help with a graphic designs project?

Hello, so I really need help. I'm not much if a social person so a few days ago in graphic designs we had to work in partners and I ended up working alone. For our project we have to construct a box, design it, and then find out how much shipping would be.

The point of this project is to put in three Pringles and send one to every student in a local high school advertising a new flavor (hypothetically of course)

I can't seem to find the price. I checked on USPS.com but they want to know how much it weights but honestly it's just a light paper box with bubble wrap and Pringles. I don't know how much it weights and I can't weigh it.

My teacher has been gone for 4 days and the project is due when he arrives tomorrow so I need help !