 </p><pre class="codeinput">load_gaimc_graph(<span class="string">'airports'</span>)
</pre><p>For some reason, the data is stored with the negative travel time between cities.  (I believe this is so that closer cities
            have larger edges between them.)  But for a minimum spanning tree, we want the actual travel time between cities.
         </p><pre class="codeinput">A = -A;
</pre><p>Now, we just call MST and look at the result. T = mst_prim(A); This command means we can't run the demo, so it's co