A married couple (filing a joint return) have a child age 7, a child age 12, and a full-time college student child age 19. If they paid $6,000 in tuition for their 19 year old child to go to work and their adjusted gross income for 2016 was $112,017, what is the amount of their child tax credit for 2016? Explain how the married couple could have increased their after tax earnings (money) by actually earning slightly less income in 2016