4. Computing and interpreting average tax rates In a hypothetical economy, Nick earns $31,000, Rosa earns $62,000, and Tim earns $93,000 in annual income. The following table shows the annual taxable income and tax liability for these three single individuals. For example, Nick, who earns $31,000, owes $8,060 in taxes. Use the tax liability figures provided to complete the following table by computing the average tax rate for Nick, Rosa, and Tim with an annual income of $31,000, $62,000, and $93,000, respectively. Taxable Income Tax Liability Average Tax Rate Taxable Income (Dollars) (Dollars) (Percent) Nick 31,000 8,060 Rosa 62,000 9,920 Tim 93,000 10,230 The income tax system for this country isNick 31,000 proportional Rosa 62,000 regressive Tim 93,000 progressive The income tax system for this country is