Ann consumes five goods. The prices of all goods are fixed. The price of good x is px. She spends 25 percent of her income on good x, regardless of the size of her income.
a) Show that her income elasticity of demand of good x is the same for any level of income, and determine its value.
b) Would the value of the income elasticity of demand for x be different if Ann always spends 60 percent of her income on good x?