Greg and Barbara, a married couple with an AGI of $80,000, have three children who are full-time

Question:

Greg and Barbara, a married couple with an AGI of $80,000, have three children who are full-time college students. They pay $6,000 for tuition annually for each child. They have one son who is a sophomore in college and another son who is a senior. Their daughter is a graduate student. How much can Greg and Barbara claim for education credits for 2013?