Because bagels and cream cheese are often eaten together, they are complements.

a. We observe that both the equilibrium price of cream cheese and the equilibrium quantity of bagels have risen. What could be responsible for this pattern: a fall in the price of flour or a fall in the price of milk? Illustrate and explain your answer.

b. Suppose instead that the equilibrium price of cream cheese has risen but the equilibrium quantity of bagels has fallen. What could be responsible for this pattern: a rise in the price of flour or a rise in the price of milk? Illustrate and explain your answer.