We learned the 'income effect' of a decrease in the price of X is measured:
a) by the change in quantity demanded of X resulting from a change in real income due to the price change.
b) by the change in quantity demanded of X resulting from a change in consumer preferences.
c) by the change in quantity supplied of X resulting from a change in producer costs.
d) by the change in quantity supplied of X resulting from a change in technology.