courts. See Mosley v. Wilson, 102 F.3d 85, 92 (3d Cir.1996) (“If the highest court has not spoken to the issue, we can garner assistance from the decisions of the state’s intermediate appellate courts in predicting how the state’s highest court would rule”). It is a settled principle of Wisconsin law that “[personnel policies, offering stated benefits in exchange for the employee’s service, are binding contracts upon the substantial performance of the requested services.” Demerath v. Nestle Co., 121 Wis.2d 194, 358 N.W.2d 541, 543 (1984). In other words, employment benefits plans are unilateral contractual offers by the employer which an employee accepts by “substantially performing” his or her employment. See Compton v. Shopko Stores, Inc., 93 Wis.2d 613, 287 N.W.2d 720, 726 (1980) (<HOLDING>); Zwolanek v. Baker Manufacturing Co., 150 Wis.
holding that performance of employment services constituted acceptance of the offer of participation in bonus plan and a binding unilateral contract was thereby formed holding that performance may be valid acceptance holding that complete performance of contract constituted acceptance holding that a valid contract requires acceptance of an offer recognizing that generally    with supposed unilateral contracts  if the offeror expressly reserves the power to revoke the offer until the offerees performance is complete then the offer is illusory and cannot give rise to a unilateral contract but noting exceptions