If the questioner is asking what speed should you fly to go as far a possible on a given bag of fuel then it will be less that 60 kt.
John: I must be loosing it - please explain. At above or below 60 kts your range in still air will be less? Therefore, with a tail wind your range will still be less above or below 60 kts, but obviously more than still air range at whatever speed you are flying!
With a headwind I accept things become more complicated - headwind offset by greater speed but offset by reduced still air range.