Categorize the companies based on their ownership status as private or public.
Twitter, SpaceX, Tesla
Private held : Twitter, SpaceX
Public : Tesla
<START_INST>Categorize the companies based on their ownership status as private or public.
Twitter, SpaceX, Tesla<END_INST><START_CTX><END_CTX><START_A>Private held : Twitter, SpaceX
Public : Tesla<END_A>