Answer:
2.5
Explanation:
If Christine now attends twice as many concerts, her percent increase in demand for concerts was 100%. Christine's income elasticity of demand for concerts is given by the percentage change in demand divided by the percentage change in income:
[tex]E = \frac{\%D}{\%I}=\frac{100\%}{40\%}\\ E=2.5[/tex]
Christine's income elasticity of demand for concerts is 2.5.