(

a) In any case of separation or desertion of a parent or parents from a child or children that results in aid under

Chapter 2 (commencing with

Section 11200) of Part of Division of the Welfare and Institutions Code being granted to that family, the noncustodial parent or parents shall be obligated to the county for an amount equal to the amount specified in an order for the support and maintenance of the family issued by a court of competent jurisdiction. (

b) The local child support agency shall take appropriate action pursuant to this

section as provided in subdivision (

l) of

Section 17400. The local child support agency may establish liability for child support as provided in subdivision (

a) when public assistance was provided by another county or by other counties. (

c) The amount of the obligation established for each parent with a liability under subdivision (

a) shall be determined by using the appropriate child support guideline currently in effect and shall be computed as follows:

(1) If one parent remains as a custodial parent, the support shall be computed according to the guideline.

(2) If the parents reside together and neither father nor mother remains as a custodial parent, the guideline support shall be computed by combining the noncustodial parents’ incomes. The combined incomes shall be used as the high earner’s net monthly disposable income in the guideline formula. Income shall not be attributed to the caretaker or governmental agency. The amount of guideline support resulting shall be proportionately shared between the noncustodial parents based upon their net monthly disposable incomes.

(3) If the parents reside apart and neither father nor mother remains as a custodial parent, the guideline support shall be computed separately for each parent by treating each parent as a noncustodial parent. Income shall not be attributed to the caretaker or government agency. (

d) A parent shall pay the amount of support specified in the support order to the local child support agency.