Reference numeral 31a represents the maximum supply power in summer which can be supplied by {HEAD ~ all operable power stations} possessed by {TAIL ~ an electric power company}, and reference numeral 31b represents the maximum supply power in winter 
possessed by
Reference numeral 31a represents the maximum supply power in summer which can be supplied by { HEAD ~ all operable power stations } possessed by { TAIL ~ an electric power company } , and reference numeral 31b represents the maximum supply power in winter
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH