Final answer:
Income elasticity of demand determines if a good is a normal or inferior good based on whether the demand for the good increases or decreases as income rises. Nothing specifically must be true about the income elasticity of demand of another good if one is an inferior good, as each good's elasticity is independent.
Step-by-step explanation:
The income elasticity of demand is an economic concept that measures how the quantity demanded of a good changes in response to changes in consumer income. For most products, a rise in income will lead to an increase in the quantity demanded, and such products are considered normal goods. Conversely, some goods see a decrease in demand as income increases; these are called inferior goods. An example of this would be individuals with higher incomes buying fewer hamburgers and more steak, or swapping cheap wine for imported beer as their income rises.
If the income elasticity of demand for one good is negative, indicating an inferior good, nothing specific must be inherently true about the income elasticity of another good you buy. Each good is independent, and the income elasticity for other goods can vary. They can also be inferior, normal, or even luxury goods with high positive income elasticity of demand, depending on how demand changes with respect to income for those particular items.