In 2015, Elaine paid $2,800 of tuition and $600 for books for her dependent son to attend

Question:

In 2015, Elaine paid $2,800 of tuition and $600 for books for her dependent son to attend State University this past fall as a freshman. Elaine files a joint return with her husband. What is the maximum American opportunity credit that Elaine can claim for the tuition payment and books in each of the following alternative situations?
a) Elaine's AGI is $80,000.
b) Elaine's AGI is $168,000.
c) Elaine's AGI is $184,000.