! Beasley "Animal feed"
! http://people.brunel.ac.uk/~mastjjb/jeb/or/moreip.html
! "Linear Programming"
min 40x1 + 60x2 + 0x3
st
 x1 + x2 + x3 = 1
100 x1 +200 x2 > 90
 80 x1 +150 x2 > 50
 40 x1 + 20 x2 > 20
 10 x2 > 2
end