(Figure: Hourly Wage and Hours of Labor I) Which of the following statements is (are) TRUE?

I. At a wage above $18, the income effect dominates the substitution effect.
II) At a wage below $18, the substitution effect dominates the income effect.
III) At a wage above $18, the substitution effect dominates the income effect.
IV) At a wage below $18, the income effect dominates the substitution effect.