Susan and Stan Britton ate a married couple who file a Joint income tax return, where the tax rates are based on the tax table 3.5. Assume that their taxable income this year was $414,000. Round your answers to two decimal places. What is their federal tax liability? What is their marginal tax rate? What is their average tax rate? Susan and Stan Britton ate a married couple who file a Joint income tax return, where the tax rates are based on the tax table 3.5. Assume that their taxable income this year was $414,000. Round your answers to two decimal places. What is their federal tax liability? What is their marginal tax rate? What is their average tax rate