The cross-price elasticity of demand refers to how the demand for a good should respond when the price of that good changes.
In this, the substitutes and the complementary goods are considered
In the case of substitutes goods, it shows a positive relationship between the demand and the price of a good. So, the cross-price elasticity of demand is positive
Whereas in the case of the complementary goods, it shows an inverse relationship between the demand and the price of a good. So, the cross-price elasticity of demand is negative
