!Keyword: path formulation, networks, telephone network;
! Call routing in a telephone network;
MAX     P1SEADNV + P2SEADNV + P1SEACHI + P2SEACHI + P1SEAATL
      + P2SEAATL + P1SEAMIA + P2SEAMIA + P1DNVCHI + P2DNVCHI
      + P1DNVATL + P2DNVATL + P1DNVMIA + P2DNVMIA + P1CHIATL
      + P2CHIATL + P1CHIMIA + P2CHIMIA + P1ATLMIA
SUBJECT TO
! The link capacity constraints;
  LSEADNV)  P1SEADNV + P2SEACHI + P2SEAATL + P2SEAMIA + P1DNVCHI
          + P2DNVATL + P2DNVMIA + P2CHIATL + P2CHIMIA <=   95
  LSEACHI)  P2SEADNV + P1SEACHI + P1SEAATL + P1SEAMIA + P1DNVCHI
          + P2DNVATL + P2DNVMIA + P2CHIATL + P2CHIMIA <=   80
  LDNVATL)  P2SEADNV + P2SEACHI + P2SEAATL + P2SEAMIA + P2DNVCHI
          + P1DNVATL + P1DNVMIA + P2CHIATL + P2CHIMIA <=  200
  LCHIATL)  P2SEADNV + P2SEACHI + P1SEAATL + P1SEAMIA + P2DNVCHI
          + P2DNVATL + P2DNVMIA + P1CHIATL + P1CHIMIA <=  110
  LATLMIA)  P1SEAMIA + P2SEAMIA + P1DNVMIA + P2DNVMIA + P1CHIMIA
          + P2CHIMIA + P1ATLMIA <=  105
! The demand constraints;
  DSEADNV)   P1SEADNV + P2SEADNV <=   10
  DSEACHI)   P1SEACHI + P2SEACHI <=   20
  DSEAATL)   P1SEAATL + P2SEAATL <=   38
  DSEAMIA)   P1SEAMIA + P2SEAMIA <=   33
  DDNVCHI)   P1DNVCHI + P2DNVCHI <=   42
  DDNVATL)   P1DNVATL + P2DNVATL <=   48
  DDNVMIA)   P1DNVMIA + P2DNVMIA <=   23
  DCHIATL)   P1CHIATL + P2CHIATL <=   90
  DCHIMIA)   P1CHIMIA + P2CHIMIA <=   36
  DATLMIA)   P1ATLMIA <=   26
 END

