Department of Operations Research, Aarhus University, Ny Munkegade, Building 1530, DK-8000 Aarhus C, Denmark;Department of Genetics and Biotechnology, Aarhus University, P.O. Box 50, DK-8830 Tjele, Denmark;Department of Business Studies, Aarhus University, Fuglesangs Allé 4, DK-8210 Aarhus V, Denmark