(a) If the parents of a resident younger than 18 years of age are divorced, the fee charged each parent for the cost of the resident's support, maintenance, and treatment is determined by that parent's own income.
(b) If the divorced parents' combined fees exceed the maximum fee authorized under the fee schedule, the department shall equitably allocate the maximum fee between the parents in accordance with department rules, but a parent's fee may not exceed the individual fee determined for that parent under Subsection (a).