In City of Philadelphia v. Fraternal Order of Police, Lodge No. 5, 564 Pa. 290, 299, 768 A.2d 291, 296-97 (2001), our supreme court stated: "Our definition of what constitutes 'an excess of an arbitrator's powers' is far from expansive." Pennsylvania State Police v. Pennsylvania State Troopers Association, 559 Pa. 586, 741 A.2d 1248, 1251 (1999). Essentially, if the acts the arbitrator mandates the employer to perform are legal and relate to the terms and conditions of employment, then the arbitrator did not exceed her authority. Id. Act 111 has defined "terms and conditions of employment" as "including compensation, hours, working conditions, retirement, pensions and other benefits...." 43 P.S. 217.1. Finally, we have stressed that a mere error of law will not support a finding that the arbitrator exceeded her powers. Pennsylvania State Police, 741 A.2d at 1251.