Stay at home mom of two, 1of which went with her dad, he wants support, NOW WHAT??

My 15yr old daughter went to live with her dad, now he wants cs and I now have the luxury of being home with my 8yr son. So I'm not working if you can call it that. He sued for cs and back support and won. He has an undocumented 14k in arrears, how do I now counter this with what he actually owes?

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