1. a Department of Industrial and Operations Engineering , University of Michigan , Ann Arbor, MI, 48109-2117, USA E-mail:
2. b School of Industrial and Systems Engineering, Georgia Institute of Technology , Atlanta, GA, 30332-0205, USA E-mail:
3. c John M. Olin School of Business, Washington University in St. Louis , St. Louis, MO, 63130-4899, USA E-mail: