In re Christina A. (1989) 213 Cal.App.3d 1073, involved the constitutionality of section 361.5, subdivision (b)(2), which permits denial of reunification services where the parent is mentally incapable of utilizing the services. The Christina A. court held: "We perceive no improper purpose underlying the statute. The stated purpose of section 361.5, subdivision (b) is to exempt from reunification services those parents who are unlikely to benefit. This purpose is related to that of the juvenile law itself--to ensure the well-being of children whose parents are unable or incapable of caring for them by affording them another stable and permanent home within a definite time period. Although the goal of the juvenile law is to reunite children with their parents whenever possible, this reunification must be accomplished within 18 months from the time the child is originally taken from his or her parents' custody. ( 366.25, subd. (a).) This strict time frame, in turn, is a recognition that a child's needs for a permanent and stable home cannot be postponed for an extended period without significant detriment. " (Id. at pp. 1079-1080.) Section 361.5, subdivision (b) was rationally related to these purposes and it was reasonable for the state to distinguish between individuals who could benefit from the services and those who could not. (Christina A., at pp. 1079-1080.)