e. In other words, if v1, v2, v3 are the
               vertices of a plate, then

                 ( v2 - v1 )  x  ( v3 - v2 )

               points in the outward normal direction. Here
               &quot;x&quot; denotes the vector cross product operator.

   the call:

      pltvol = <b>cspice_pltvol</b>( vrtces, plates )

   returns:

      pltvol   The function returns the volume of the spatial region bounded
               by the plates.

               [1,1] = size(pltvol); double = class(pltvol)
