Suppose Denise purchases only two goods, x and y. Initially, px = 2, py = 3, and i = 20. Then, px = 4, py = 6, and i = 30. If x is normal and y inferior for her, Which of the following is true?
a) Denise's income elasticity of demand for good x is positive.
b) Denise's income elasticity of demand for good y is positive.
c) Denise's income elasticity of demand for good x is negative.
d) Denise's income elasticity of demand for good y is negative.
e) Denise's cross-price elasticity of demand between goods x and y is negative.