Suppose we observe that both the equilibrium price of film cameras and the equilibrium quantity of film cameras have fallen. Which of the following could be responsible for this?

Question

Quizplus · Accepted Answer

If consumers' preferences have shifted toward digital cameras, then there is a decrease in demand for film cameras. Given the law of demand, a decrease in demand leads to a decrease in both price and quantity. Therefore, A is the best answer. 
B is incorrect because technological advances in film camera production would make it cheaper to produce film cameras, which would lead to an increase in supply and a decrease in price but an increase in quantity. 
C is incorrect because a pay raise for camera workers would increase the cost of production and lead to an increase in the price of film cameras, but would not affect quantity. 
D is incorrect because an increase in the price of digital cameras would shift demand in favor of film cameras, leading to an increase in the equilibrium price and quantity of film cameras.

Suppose We Observe That Both the Equilibrium Price of Film