10 Because macaroni and cheese are often eaten together, they are complements.

a We observe that both the equil ibrium price of cheese and the equilibrium quantity of macaroni 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 cheese has risen but the equ ilibrium quantity of macaroni 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.