1. Socio-economic Research Center; Central Research Institute of Electric Power Industry; 1-6-1 Otemachi, Chiyoda-ku Tokyo 100-8126 Japan
2. Graduate School of Decision Science and Technology; Tokyo Institute of Technology; W9-41, 2-12-1, Ookayama, Meguro-ku Tokyo 152-8552 Japan
3. New Mexico Institute of Mining and Technology; Management Department; Socorro NM 87801 USA