Can anyone help me with this?

Suppose the government has imposed a price ceiling on sliced sandwich bread. Which of the following events could transform the price ceiling from one that is binding to one that is not binding?

a. An increase in the price of flour, which is used to make bread.

b. A decrease in the price of lunch meat.

c. A decease in the price of unsliced bread, which people consider as a

substitute for sliced bread.

d. An decrease in the price of peanut butter and jelly.