John and Mary paid $7900 in qualified employment-related expenses for their three young children eho live with them in thier household. Mary received $1,800 of dependent care assistance from her employer, which was properly excluded from gross income. The couple had $5,700 of AGI earned by both equally. What amount of child and dependent care tax credit can they claim on their Form 1040? How would it differ if the couple had an AGI of $36,00 earned entirely by John.