     <li>
          <a href = "p23_region.m">p23_region.m</a>, 
          returns the region type for problem 23.
        </li>
        <li>
          <a href = "p23_title.m">p23_title.m</a>, 
          prints a title for problem 23.
        </li>
        <li>
          <a href = "p24_default.m">p24_default.m</a>, 
          sets default values for problem 24.
        </li>
        <li>
          <a href = "p24_exact.m">p24_exact.m</a>, 
          sets the exact integral for problem 24.
        </li>
      