Using Table 3.7, calculate the marginal and average tax rates for a single taxpayer with the following incomes: (Do not round intermediate calculations. Round your answers to 1 decimal place.) Answer is complete but not entirely correct Income Marginal Tax Rate Average Tax Rate a. $ 20,000 b. 50,000 c. 300,000 d.3.000,000 15.00 % 25.0 % 33.0 % 35.0 % 12.7 % 16.7 % 27.6 % 34.2 x%