(*x=almonds;  y=oats*)

(*Costs of almonds and oats*)
cx=1;cy=1.2;
constraints=8x+6y≥11&&4x+12y≥16&&x≥0&&y≥0
feasible=RegionPlot[constraints,{x,0,2},{y,0,2},PlotPoints->100]

Manipulate[Show[feasible,Plot[c/cy-cx/cy x,{x,0,5},PlotRange->{0,5},PlotStyle->{Thick,Black}]],{{c,2},0,4}]

lines=Plot[Table[c/cy-cx/cy x,{c,0,1.9,.1}],{x,0,5},PlotStyle->Black];
opt=Plot[c/cy-cx/cy x/.c->1.9,{x,0,2},PlotStyle->Red];
Show[feasible,lines,opt]
Minimize[{cx x+cy y,constraints},{x,y}]

sol=Solve[8x+6y==11&&4x+12y==16]
cx x+cy y/.sol

Plot3D[cx x+cy y,{x,0,2},{y,0,2},RegionFunction->Function[{x,y},8x+6y≥11&&4x+12y≥16],MeshFunctions->{#3&},ColorFunction->"DarkRainbow"]