Martina is single and has two children in college. Matthew is a sophomore and Christine is in her fifth year of college. Martina pays $3,600 in tuition and fees for Matthew, $700 for textbooks, and $2,000 for his room and board. Christine's tuition and fees are $4,800, her textbooks are $550, and her room and board expenses are $1,800. Martina's adjusted gross income is $63,000.

a. What amount can Martina claim as a tax credit for the higher education expenses she pays?

b. Assume that Martina’s adjusted gross income is $83,000. What amount can she claim as a tax credit for the higher education expenses she pays?