The nation of Upstandia uses kroner for money and its tax code is such that a person making 100,000 kroner per year pays 40,000 kroner per year in income taxes; a person making 200,000 kroner per year pays 70,000 kroner per year in income taxes; and a person making 300,000 kroner per year pays 90,000 kroner per year in income taxes. Upstandia’s income tax system is:

a. Progressive.

b. Regressive.

c. Proportional.