Suppose there is a linear relationship between national income and total tax revenue. If national income is $100 million, then $25 million is collected as tax revenue . If national income is $200 million, then $40 million is collected in tax revenue. What is the marginal response in tax revenue to a change in national income?
◦ -15
◦ 15
◦ 15 million
◦ 0.15 million
◦ 0.15