Final answer:
A change in the price of a substitute good, like submarine sandwiches, will shift the demand curve for hamburgers. An increase in the substitute's price leads to an increased demand for hamburgers and vice versa. Conversely, a change in the price of a complement, such as french fries, has the opposite effect.
Step-by-step explanation:
Which factor will shift the demand curve for hamburgers? The options provided include changes in the prices of substitutes (such as submarine sandwiches), the price of hamburgers themselves, the price of an input (such as ground beef), or the price of complements (like french fries). A change in the price of hamburgers itself would not shift the demand curve but rather lead to a movement along the demand curve. However, a change in the price of a substitute good (submarine sandwiches) will shift the demand curve. If the price of the substitute increases, consumers may opt to buy more hamburgers, shifting the demand curve to the right. Conversely, a change in the price of a complement good (french fries) will also shift the demand curve. If fries become more expensive, people might buy fewer hamburgers, shifting the demand curve to the left.
Consider the demand for hamburgers. If the price of a substitute good (hot dogs) increases, the demand for hamburgers would typically increase, shifting the demand curve to the right. However, if the price of a complement good (hamburger buns) also increases, this could decrease the demand for hamburgers, shifting the demand curve to the left. The final impact on the demand for hamburgers is uncertain because it depends on which effect is stronger. The interaction of these two opposing forces means we cannot tell for sure what will happen to the demand for hamburgers without additional information.