Income elasticity of demand measures the responsive-ness of demand to changes in income. Explain what is happening to demand and what kind of good is being represented in the following situations.
a. Income is rising, and income elasticity of demand is positive.
b. Income is rising, and income elasticity of demand is negative.
c. Income is falling, and income elasticity of demand is positive.
d. Income is falling, and income elasticity of demand is negative.