!Keyword:  path formulation, networks, distribution;
! Path formulation of a multi-level distribution problem;
MIN     6 AX1 + 7 AX2 + 8 AY2 + 9 AY3 + 8 BX1 + 10 BY1 
      + 7 BY2 + 8 BY3 + 10 BZ2 + 9 BZ3 + 6 BZ4
SUBJECT TO
   2)     AX1 + AX2 + AY2 + AY3 =    9
   3)     BX1 + BY1 + BY2 + BY3 + BZ2 + BZ3 + BZ4 =    8
   4)     AX1 + BX1 + BY1 =    3
   5)     AX2 + AY2 + BY2 + BZ2 =    5
   6)     AY3 + BY3 + BZ3 =    4
   7)     BZ4 =    5
END

