.. think you got it in one ..
(a) nose = single axle two wheels = 725 x 2 = 1450 kg
(b) mains = (single axle two wheels) x 2 = 6000 x 4 = 24000 kg
Taking moments about the mains ..
M = - ( 1450 x 10 ) kg.m
= - 14500 kg.m
CG = total moment/total weight
= - 14500 / (24000 + 1450)
= - 0.57 m
(ie 57 cm in front of the main axle line)
.. unless, of course, it's getting a bit late in the day and I've made a mistake ...