Answer:
a. Her AMTI is $90,000
Because her AMTI does not excéed threshold of $160,900 her AMT exemption is not phased out and she is entitled to the full exemption amount of $84,500
b Her AMTI is $180,000
Because her AMTI exceed the threshold of $160,900, she must phase out her exemption and is entitled to:
84,500 - {(180,000 -160,900) × 25% } = $ 79,725(entitlement)
c. Her AMTI is $500,000
She is not allowed to deduct any exemption amount as it is entirely phased out as shown below
$84,500 -{(500,000-160,900) × 25%} = -275. Less than zero