/* Objective function */
min: 2 xab +   xag +   xbc +   xbe + 2 xbf +   xbh +   xbi + 3 xcd + 2 xed + 3 xfc +   xfe + 3 xgf + 4 xgi + 3 xha +   xhc + 2 xhi + 3 xic + 3 xid + 4 xie;

/* Variable bounds */

a:   - xab -   xag                                                                                         +   xha                                         = -2;
b:     xab         -   xbc -   xbe -   xbf  -  xbh -   xbi                                                                                                 =  0;
c:                 +   xbc                                  -  xcd         +   xfc                                 +   xhc         +   xic                 =  3;
d:                                                             xcd +   xed                                                                 +   xid         =  5;
e:                             xbe                                 -   xed         +   xfe                                                         +   xie =  4;
f:                                     xbf                                 -   xfc -   xfe +   xgf                                                         = -5;
g:             xag                                                                         -   xgf -   xgi                                                 = -6;
h:                                             xbh                                                         -   xha -   xhc -   xhi                         = -2;
i:                                                     xbi                                         +   xgi                 +   xhi -   xic -   xid -   xie =  3;