First Author:   Arieh Gavious Ben Gurion University ariehg@bgu.ac.il   Department of Industrial Engineering & Management, Ben Gurion University Beer Sheva, 84105, Israel   972-8-6472212(Phone) 972-8-6472212(Fax) http://www.bgu.ac.il/~ariehg/ Second Author: Ramy Elitzur University of Toronto Elitzu@Rotman.Utoronto.Ca   Rotman School of Management, University of Toronto, 105 St. George St. Toronto, M5S 3E6, Canada   (416) 978-3827(Phone) (416) 971-3048(Fax)