What is the AGI limit above which each of the following taxpayers would not be eligible to receive a credit for the elderly or the disabled?

		AGI Upper Limit
a.	A single taxpayer eligible for the credit who receives $1,900 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 $3,900 of nontaxable social security benefits.