in a certain country, a couple, a and b earn a combined income of 82500. the government taxes as follows. 5% on the first 20,000; 20% on the next 30,000; and 30% on all income above 50,000.

a) calculate the average tax rate

b) calculate the marginal tax rate

c) now the government introduces an exemption for tax relief, 20,000 per person. what the now average tax rate?

d) in the case of c) calculate the marginal tax rate