When trying to calculate accurately the price elasticity of demand for corn between the
months of June and July, which of the following must not be true?
a. Income between June and July is the same
b. The price of wheat is the same between June and July
c. The price of corn is the same between June and July
d. The number of buyers for corn is the same between June and July
e. The preferences of buyers are the same between June and July