Suppose that when the average family income falls from $40,000 per year to $30,000 per year, the average family's purchase of toilet paper rises from 100 rolls to 103 rolls per year. The income elasticity of demand for toilet paper is -0.10; Toilet paper is an inferior good, and the demand for toilet paper is income inelastic. +9.7; Toilet paper is a normal good, and the demand for toilet paper is income elastic