Denial of petition for writ of mandate seeking to compel defendant to reimburse plaintiff for money expended on its employee health care costs is affirmed over claims that: 1) the trial court and defendant improperly construed and applied pertinent guidelines found in the Provider Reimbursement Manual; 2) the guidelines should not be followed because they violate statutory authority; and 3) defendant's decision is invalid since it was based on the current version of the Provider Reimbursement Manual, which was not promulgated in accordance with the Administrative Procedure Act.