Ann and Bill were on the list of a local adoption agency for several years, seeking to adopt a child. Finally, in 2015, good news comes their way, and an adoption seems imminent. They pay qualified adoption expenses of $5,000 in 2015 and $11,000 in 2016. Assume that the adoption becomes final in 2016. Ann and Bill always file a joint income tax return.

a) Determine the amount of the adoption expenses credit available to Ann and Bill, assuming that their combined annual income is $120,000. What year(s) will they benefit from the credit?

b) Assuming that Ann and Bill's modified AGI in 2015 and 2016 is $220,000, calculate the amount of the adoption expenses credit.