In order to determine which parent should have custody of the child, the trial court is to make two inquiries under Welfare and Institutions Code section 366.21, subdivision (e). The court would have to determine whether the previously noncustodial parent is now ready to assume custody without supervision. (In re Nicholas H., supra, 112 Cal.App.4th at p. 267.) Section 366.21, subdivision (e) states in part that if a minor "had been placed under court supervision with a previously noncustodial parent pursuant to Section 361.2, the court shall determine whether supervision is still necessary. The court may terminate supervision and transfer permanent custody to that parent . . . ." (see 15 "shall" is mandatory while "may" is permissive.) If the court transfers permanent custody to the previously noncustodial parent, the court "shall terminate its jurisdiction over the child." ( 361.2, subd. (b)(1).) However, "nothing in the language of section 366.21, subdivision (e) or any other applicable provision requires the juvenile court to award custody to the parent with whom the child has been placed subject to supervision during the proceedings." (In re Nicholas H., supra, 112 Cal.App.4th at p. 267, fn. 5.) Rather, section 361.2, subdivision (b)(3) directs that "at review hearings held pursuant to Section 366" the court must determine "which parent, if either, shall have custody of the child." (Ibid.; In re Nicholas H., at p. 267.) When making a custody determination in any dependency case, the court's overriding consideration must be the minor's best interests. (In re Nicholas H., at p. 268.) "Thus, for example, a finding that neither parent poses any danger to the child does not mean that both are equally entitled to half custody, since joint physical custody may not be in the child's best interests for a variety of reasons. By the same token, a finding that the parent from whom custody was removed no longer poses a risk of detriment or that the parent whose custody has been subject to supervision no longer requires supervision is relevant to, but not necessarily determinative of, the best interests of the child." (Ibid.) A trial court's ruling should not be disturbed on appeal unless an abuse of discretion is clearly established. (In re Michael B. (1992) 8 Cal.App.4th 1698; In re Corey (1964) 230 Cal.App.2d 813, 832.) As one court has stated, when a court has made a custody determination in a dependency proceeding, "'a reviewing court will not disturb that decision unless the trial court has exceeded the limits of legal discretion by making an arbitrary, capricious, or patently absurd determination .'" (In re Geoffrey G. (1979) 98 Cal.App.3d 412, 421; see In re Stephanie M. (1994) 7 Cal.4th 295, 318-319.) "'The appropriate test for abuse of discretion is whether the trial court exceeded the bounds of reason. When two or more inferences can reasonably be deduced from the facts, the reviewing court has no authority to substitute its decision for that of the trial court.'" (Walker v. Superior Court (1991) 53 Cal.3d 257, 272, quoting Shamblin v. Brattain (1988) 44 Cal.3d 474, 478-479.)