Do the given call working with imaginary dancers (i.e., Phantoms). Assume that
the Phantoms are in whatever position, have whatever facing direction, and are
of whatever sex is necessary in order to execute the given call. The call is
then danced with both the dancers and the Phantoms participating. Keep track
of the Phantoms that you are working with and reserve space for them at the
completion of the call.
EN: 20