The Law of Supply requires a pre-condition for it to be valid. What is that pre-condition?

law that states that, all other factors being equal, as the price of a good or service increases, the quantity of goods or services that suppliers offer will increase, and vice versa. The law of supply says that as the price of an item goes up, suppliers will attempt to maximize their profits by increasing the quantity offered for sale.

answer; i believe that the correct answer is ( troxel v. granville);