Apologies for what is probably a dumb question, but I cannot find the answer on ba.com. I am looking at booking a flight for a family member (who has no status, and therefore no extra bag allowance) and they will need to carry more than the 1 bag allowed. The trip is in Euro Traveller with a domestic feeder.

If they purchase an extra bag, will this cost 4 x the extra bag cost (i.e. 2 x Euro Traveller and 2 x domestic) or 2 x the extra bag cost (i.e. 2 x Feeder+Euro Traveller)?

Thanks!