1. Department of Electrical and Computer Engineering & Coordinated Science Laboratory, University of Illinois Urbana-Champaign, Urbana, Illinois 61801;
2. Department of Electrical and Computer Engineering & Institute for Systems Research, University of Maryland, College Park, Maryland 20740;
3. Cornell SC Johnson College of Business & Nolan School of Hotel Administration, Ithaca, New York 14853;
4. Institute for Data, Systems, and Society, Department of Civil and Environmental Engineering, Operations Research Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139