Question 27 of 75. A refundable credit reduces the taxpayer's Income before determining tax liability. O Tax liability, and may even exceed the tax liability. Income before determining tax liability, and may even increase the refund. Tax liability, but may not exceed the tax liability. Mark for follow up Question 28 of 75. How much of the American Opportunity Credit (AOC) may be refundable? 10% 25% 40% 55% Mark for follow up