Assuming that an AGI limitation does not apply, what amounts of credit for the elderly or the disabled would be permitted in each of the following instances?

$\backslash$table$[[$a A single taxpayer eligible for the credit who receives $$1,500$ of nontaxable$],[$social security benefits.$],[$b$.$ Taxpayers filing a joint return for which one taxpayer is eligible for the credit$],[$and the taxpayers have received no social security benefits.$],[$C$.$ Taxpayers filing a joint return, and both are eligible for the credit and$],[$received $$3,500$ of nontaxable social security benefits.$]]$