(1) The annual rate of child support payable for a child for a day in a child support period is assessed under this Subdivision if:
(a) both parents of the child are to be assessed in respect of the costs of that child; and
(b) at least one of the parents of the child is to be assessed in respect of the costs of another child in another child support case.
(2) For the purposes of paragraph (1)(b), a parent is taken to be assessed in respect of the costs of another child in another child support case if the parent is liable to pay child support for that child under an administrative assessment under the law of a reciprocating jurisdiction.