Determine the retirement savings contributions credit in each of the following independent cases. Use Table $9-2.$

$\backslash$table$[[,\backslash$table$[[$Retirement$],[$Savings$],[$Contributions$],[$Credit$]]],[$a$.$ A married couple filing jointly with modified AGI of $$37,500$ and an IRA contribution of $$1,800.,],[$b$.$ A married couple filing jointly with modified AGI of $$58,000$ and an IRA contribution of $$1,900.,],[$c$.$ A head of household taxpayer with modified AGI of $$33,000$ and Roth IRA contribution of $$1,990.,],[$d$.$ A single taxpayer with modified AGI of $$12,000$ and an IRA contribution of $$2,800.,]]$