Answer:
Substitution
Explanation:
Principle of subsitution states that no consumer should buy a product for a high price of he can get an alternative (duplicate) that is of a cheaper price.
Substitutes are alternatives that provide similar satisfaction to the customer.
When the price of one product goes up the customer has a choice of going for an alternative.
For example honey and sugar are substitutes. When the price of one goes down people will go for the cheaper alternative. This acts as a price control mechanism.
