Answer:
.a.rent on the restaurant building.
Step-by-step explanation:
Variable costs are costs that changes with the level of production.
If David extends opening hours, hours worked by the servers, energy costs, hours worked by cooks and ingredients used in preparing food would increase. Therefore, they are all variable cost.
Fixed cost are costs that do not change with production level.
If David extends opening hours, the rent paid isn't affected in any way.
I hope my answer helps you.