Use Table 3.6. (Do not round intermediate calculations. Enter the average tax rate as a percent rounded to 1 decimal place.) a. What would be the marginal tax rate for a married couple with income of $90,900 ? b. What would be the average tax rate for a married couple with income of $90,900 ? c. What would be the marginal tax rate for an unmarried taxpayer with income of $90,900? d. What would be the average tax rate for an unmarried taxpayer with income of $90,900? TABLE 3.6 Porsonal tax rates, 2018