Rates for a married taxpayer filing separately are $10\%$ of taxable income up to $$8,375$ and $15\%$ thereafter up to $$34,000.$ Rates for a couple filing a joint return are $10\%$ of taxable income up to $$16,750$ and $15\%$ thereafter up to $$68,000.$ Patrick and Kelly O'Day are figuring their tax both ways for comparison before deciding which way to file. Patrick earned $$15,000$ and Kelly earned $$35,000.$ The standard deduction for a married couple filing jointly is $$12,200.$ The standard deduction for each married taxpayer filing separately is $$6,100.$ Exemption for each taxpayer is $$3,900.$

a$.$

Compute the amount of tax the O'Days will owe if they file a joint return.

b$.$

Compute the amount of tax the O'Days will owe if they file two separate returns. $($For your answer, add the individual returns together.$)$