You can put the datum anywhere you like. So in this case I am going to make the datum on the main wheels.
2 x 725 = 1450 kg x arm to main wheels 10 m = -14500
4 x 6000 = 24000 kg x zero arm = zero moments = 0
BEM = 25450 CoG 14500/25450 = .57 metres (57 cms in front of main wheels)