As you know, the Pressure is calculated by: force divided by area.
Therefore, plugging in our known values:
Force is equal to 6000Kg then covert this to Newtons = 6000 kg x 9.81 N = 58680
Area is 4*(.1m^2) = .4m^2
Pressure: 58680 N / .4 m^2 = 150,000 N/m^2