var a >= 0 <= 20;
var b >= 0 <= 40;
maximize f: 120*a +  80*b;
s.t. c3 : a*20 + b*10 <= 500;
solve;
display f ,a, b;
end;

______________________
var a >= 0; --pszenica
var b >= 0 <= 100; -- ryż
maximize f: 20*a + 50*b;
s.t. c1: a >= 0.8*(a+b);
s.t. c2: 2*a + 4*b <= 240;
solve;
display f,a,b;
end;


____________________________
var a >= 0;
var b >= 0;
var c >= 0;
maximize f: 300*a + (8*50)*b - 10* c;
s.t. c1: 12*a + 20*b = c;
s.t. c2: a + b <= 100;
s.t. c3: 10*a <= 560;
s.t. c4: 8*b <=480;
s.t. c5: c <=1400;
solve;
display f,a,b,c;
end;
______________________________

var st1 >= 0; 
var st2 >= 0;
var st3 >= 0;
minimize f: 200*st1 + 150*st2 + 400*st3;
s.t. c1: st1+st2+st3 <= 5000;
s.t. c2: 0.28*st1 + 0.14*st2 + 0.1*st3 <= 0.14;
s.t. c3: 0.1*st1 + 0.12*st2 + 0.06*st3 <= 0.08;
s.t. c4: 0.3*st1 + 0.2*st2 + 0.3*st3 >= 0.25;
s.t. c5: 0.1*st1 + 0.1*st2 + 0.15*st3 >= 0.12;
solve;
display f,st1,st2,st3;
end;


_________________TODO
var x1 >=0;
var x2 >=0;
var y11 >=0;
var y12 >=0;
var y21 >=0;
var y22 >=0;
maximis


minimize f: 8(y11+y21) + 6(y12 + y22) - 10x1 - 8x2;
s.t. c1: y11 + y12 <= 2;
s.t. c2: 0.28*st1 + 0.14*st2 + 0.1*st3 <= 0.14;
s.t. c3: 0.1*st1 + 0.12*st2 + 0.06*st3 <= 0.08;
s.t. c4: 0.3*st1 + 0.2*st2 + 0.3*st3 >= 0.25;
s.t. c5: 0.1*st1 + 0.1*st2 + 0.15*st3 >= 0.12;
solve;
display f,st1,st2,st3;
end;