For a mall, I would use Ordinary Hazard, Group 2, at 0.2 gpm/sq.ft.. This is in line with NFPA 13, A-2-1.2.2 which lists Mercantile occupancies in Ordinary, group 2.
Parking lot? I don't know. NFPA has auto parking (garages) in Ordinary, group 1, at 0.15 gpm/sq.ft.
The densities of course change with changing the design area. See NFPA 13 for the chart.