The computed minimum f0 (f0Min), maximum f0 (f0Max) and mean f0 (f0Mean) of each utterance
(in Hertz) within all attitude types was/were(?) standardized as follows:... 

There are three things before "was/were", but everyone is singular, so, should I use "was" or "were"?

The computed minimum f0 (f0Min), maximum f0 (f0Max) and mean f0 (f0Mean) of each utterance (in Hertz) within all attitude types was/were(?) standardized as follows:...

There are three things before "was/were", but everyone is singular, so, should I use "was" or "were"?

The computed minimum f0 (f0Min), maximum f0 (f0Max) and mean f0 (f0Mean) of each utterance (in Hertz) within all attitude types was/were(?) standardized as follows:...

There are three things before "was/were", but everyone is singular, so, should I use "was" or "were"?

The computed minimum f0 (f0Min), maximum f0 (f0Max) and mean f0 (f0Mean) of each utterance
(in Hertz) within all attitude types was/were(?) standardized as follows:... 

There are three things before "was/were", but everyone is singular, so, should I use "was" or "were"?