title: Matlab linprog yields an unbounded result to a bounded model
body: <pre><code>clear
  A=[-1 0 -1 0; 0 -1 0 -1; 1 1 0 0; 0 0 1 1];
  b=[-50 -70 80 45];
  f=[0.5; 0.6; 0.4; 0.55];
  options = optimoptions('linprog','Algorithm','dual-simplex');
  [x,fval,exitflag,output] = linprog(f,A,b,[],[],[],[],options);
  </code></pre>
  
  <p>Code shown above produces an unbounded result <code>Problem is unbounded</code> where Lindo and Excel Solver find the optimal objective function value which is 62.5 </p>