Taking into account the aging population, not to mention younger people with hearing loss from loud music, a) is too short. People hard of hearing need a few words to accommodate to the the speaker's voice and a little redundancy to make sure that what they think they heard is what they heard. So b) is much better.
Meets the criteria for the hard of hearing but a bit silly to thank me for calling til they know what I have to say. And I don't need John's name if he's just going to pass me on to another number.
Gak. Hang up now. Call somebody else.
Mike Spencer Nova Scotia, Canada