In the sell-or-process-further decision,
  a.  joint costs are always relevant.
  b.  total costs of joint processing and further processing are relevant.
  c.  all costs incurred prior to the split-off point are relevant.
  d.  the most profitable outcome can be to further process some separately identifiable products beyond the split-off point, but sell others at the split-off point.
  e.  none of the above.