Harbour={ idH(pk), country, Hname,location}

Ship={idS(pk) , Shipname, captain, capacity}

Captain is a surname

Capacity={capacity_type(pk) , from_cap, to_cap}

For example small from 200-300

Medium 301- 800

Docked (idD(PK) , harbour, ship, since, till, accepted_by)

Accepted_by is a surname of office worker who registered the visit

please write a query

Show names of captains which are also names of harbour office workers.