1. Grilled-Cheese Business Break-down of Costs
For a grilled-cheese sandwich you need: bread, cheese, butter, and a paper towel.
I researched each of these, and found the cheapest prices to be the following:
Bread: $1.44/loaf – makes 12 sandwiches
Cheese: $3.50/bag – makes 10 sandwiches
Butter: $3.75/lb. – makes 40 sandwiches
Paper Towels: $0.99/roll – makes 120 sandwiches
By dividing out the number of sandwiches made for each ingredient, I could get a unit cost:
Bread: $0.12/sandwich
Cheese: $0.35/sandwich
Butter: $0.09/sandwich
Paper Towels: $0.01/sandwich
Total Cost per Sandwich: $0.57/sandwich

2. Determining the Cost Curve Equation
Remember: Total Cost = # x Variable Cost + Fixed Cost
So, if the variable cost per unit is $0.57, then the # of units would be the variable: x
Our fixed costs are $15 (which covers rent to the school and advertising time bought from the principal)
This makes our cost curve equation:
y = 0.57x + 15
Where the slope is 0.57 (57/100) and the y-intercept is (0, 15)