Final answer:
The total cost for stamps at the post office is the dependent variable, while commission could be either dependent or independent depending on the context.
Step-by-step explanation:
In the context of the question, the total cost for stamps at the post office would be considered the dependent variable. This is because the cost of stamps depends on factors such as the weight of the mail, the destination, and the type of service (regular mail, priority mail, etc.). The independent variable would be the factors that determine the cost of stamps.
As for commission, it could be either independent or dependent, depending on the context. If the commission is based on a fixed rate or a predetermined formula that does not vary with other factors, then it would be an independent variable. However, if the commission is calculated based on the total cost of stamps or some other variable, then it would be a dependent variable.