Marginal corporate tax rates The 2009-2013 taxable earnings of Peter & Son Plumbers were $57,000, $64,000, $66,500, $75,250, and $79,350, respectively. Use the tax schedules presented in Table 2.1 to answer the following questions: a. What is the relationship between the tax liability and the marginal tax rate over the five-year period? b. What is the relationship between the taxable earnings and the marginal tax rate for the 2009-2013 taxable earnings?