Alright, so I'm playing the bassline to Interpol's "Evil" and I just can't figure out what key it would be in.

The notes are F->Bb->A->D->A. I can barely figure out key when I do the chords to songs, so this is way hard. Can I even figure out the key from the bassline or do I have to have the whole song? Thanks in advance!
The key of F.

F(root note), Bb (Fourth), A(Major third), D(Minor Sixth).
Quote by Rick540
I play in drop F. When I chug on the 6th string the floor splits open and satan crawls out.
maybe Bb major...

F being the 5, Bb being the root, A being the 7 and D being the 3rd