You sell sandwiches from a food truck. You have two types of inputs: ingredients and wages for a single worker. You buy the necessary ingredients (bread, ham, cheese, etc.) from the supermarket every morning. Your ingredient cost is $150 for 100 sandwiches, or $250 for 200 sandwiches. You sign a daily 6-hour contract with the worker, and pay him $120 at the end of each day, regardless of how many sandwiches were made and sold. Which input constitutes your variable cost?

Ingredients for the sandwiches.

Wages for the worker.

Ingredients for the sandwiches and wages for the worker.

You have no variable cost, since none of the inputs can be adjusted once you have chosen how many sandwiches to produce.