"Assume that the price of crisps rises while the equilibrium quantity falls. Explain in each of the following cases whether they are true, false or uncertain and argue with respect to the statement made:

a. An increase in the price of onion rings (a substitute for French fries)

b. A fall in the price of onion rings.

c. An increase in the price of potato bread (production-side substitute for potato crisps).

d. A fall in the price of potato bread.