How much of a nanny's income should be divided between child care and housekeeping?

[43] The mother’s proposal to set the child-care portion of the nanny’s income at 80% is very reasonable. Since she is a shift-worker, with unpredictable hours, it is reasonable and necessary for the mother to use a nanny, instead of an outside child-care provider. As a result, many of the nanny’s cooking, cleaning and laundry responsibilities are intertwined with her child-care responsibilities. The children in this case are even younger than those in Low v. Robinson (who were 9 and 5) and require more intensive child care. They are frequently in the home and housekeeping is essential to promote their well-being. The personal benefit that the mother obtains from the nanny is no more than the 20% suggested by her. The nanny is primarily there to care for the children.