Assume that the density of kerosene is 0.81 kg/litre. Conversion factor 1nm = 1.852 km.
Fuel burn in litres = 1950/0.81 = 2407 litres.
Distance in km = 320 * 1.852 = 592.6 km.
Passenger kilometres travelled = 120 * 592.6 = 71,112.
Fuel burn, in litres, per passenger per kilometer = 2407/71,112 = 0.0338.
I think that the fuel burn per 100 km mentioned by the earlier contributor is the correct figure to use. Correspondingly, fuel burn per passenger/100 km = 0.0338 * 100 = 3.38.
About a 10% saving to go then for short haul. Perhaps professionals (not this wouldhavelikedtohavebeen (too old to be a wannabee!)) with similar data for medium or longhaul could provide such data to see if B777s etc are already down to the 3 mentioned in the original post.