If the cross elasticity of demand between milk and yogurt is -1.5, then are milk and yogurt substitutes or complements?
Select one:
a. They are substitutes because when the price of yogurt increases by 10%, for example, the demand for milk decreases by 15%.
b. They are complements because when the price of yogurt increases by 10%, for example, the demand for milk increases by 15%.
c. They are substitutes because when the price of yogurt increases by 10%, for example, the demand for milk increases by 15%.