Which of the following is not an example of a barrier to entry that helps a firm maintain its monopoly power?

1 Owning land that has a large amount of the world's supply of iron ore.

2 A firm owning multiple businesses in an area allowing them to streamline production and reduce costs.

3 An increase in the minimum wage making it costlier to hire employees.

4 Supermarkets negotiating lower prices with distributors than smaller grocery stores can get.

5 A law requiring hairdressers to have a license to blow dry hair.