What is the test for determining the appropriate amount of child support under section 4055 of the California Family Code?

² Section 4057, subdivision (a) provides that the amount of child support established by the complex formula of section 4055 a formula that relies heavily on the parents' monthly disposable incomeis presumed correct. (See Mejia v. Reed (2003) 31 Cal.4th 657, 670, 3 Cal.Rptr.3d 390, 74 P.3d 166.) Under subdivision (b)(3) of section 4057, a parent with an "extraordinarily high income" need not pay child support commensurate with the formula if he or she establishes "the amount determined under the formula would exceed the needs of the children." Under subdivision (b)(5), the parent may be required to pay more than the formula if its application "would be unjust or inappropriate due to special circumstances in the particular case." A court may deem a party's substantial non-income producing assets "a special circumstance [citation] that may justify a departure from the guideline figure for support payments." (Mejia v. Reed , supra , at p. 671, 3 Cal.Rptr.3d 390, 74 P.3d 166.) (Undesignated statutory references are to the Family Code.)