!Keyword: transportation, equilibria;
MIN 20 AB2 + 50 AB3 + 70 AB4 + 52 AC2 + 55 AC3 + 57 AC4 + 12 BC2
  + 15 BC3 + 17 BC4 + 52 BD2 + 55 BD3 + 57 BD4 + 20 CD2 + 50 CD3
  + 70 CD4   ! Minimize total congestion

SUBJECT TO
   2)  -  AB2 -  AB3 -  AB4 +   AB =    0   !Definition of AB
   3)  -  AC2 -  AC3 -  AC4 +   AC =    0   ! and AC,             
   4)  -  BC2 -  BC3 -  BC4 +   BC =    0   ! BC
   5)  -  BD2 -  BD3 -  BD4 +   BD =    0   ! BD             
   6)  -  CD2 -  CD3 -  CD4 +   CD =    0   ! and CD
   7)     AB +  AC  =   6                   ! Flow out of A
   8)     AB -  BC -  BD  =    0            ! Flow through B
   9)     AC +  BC -  CD  =    0            ! Flow through C
  10)     BD +  CD =    6                   ! Flow into D
  11)     AB2 <=   2                     ! Steps in supply schedule
  12)     AB3 <=   1                          
  13)     AB4 <=   1
  14)     AC2 <=   2 
  15)     AC3 <=   1
  16)     AC4 <=   1
  17)     BC2 <=   2
  18)     BC3 <=   1
  19)     BC4 <=   1
  20)     BD2 <=   2
  21)     BD3 <=   1
  22)     BD4 <=   1
  23)     CD2 <=   2
  24)     CD3 <=   1
  25)     CD4 <=   1
END

