title: Learning more about APOPT solver
body: <p>I have a few questions about how APOPT solves MINLPs.<br></p>
  
  <ul>
  <li>What nonlinear programming method APOPT uses (interior point, trust region, etc.)?</li>
  <li>How does APOPT deal with mixed integers (B&amp;B, outer approximation,  generalized benders decomposition,etc)?</li>
  </ul>