min   8x11+ 13x12 + 25x13 + 28x14
   +  15x21+ 12x22 + 26x23 + 25x24
   +  0x31+ 6x32 + 16x33 + 17x34
   +  6x41+ 0x42 + 14x43 + 16x44
st
      x11+ x12 + x13 + x14<=180
     x21+ x22 + x23 + x24<=120
     x31+ x32 + x33 + x34=300
     x41+ x42 + x43 + x44=300
     x11+ x21 + x31 + x41=300
    x12+ x22 + x32 + x42=300
    x13+ x23 + x33 + x43=140
    x14+ x24 + x34 + x44=120
END