Total rated power ∑ PE = 40× 6kW+135× 7kW =1185kW.
Active power pjs = ∑ PE× kx =1185kw× 0.35 (for the required coefficient, please refer to page 24 of National Architectural Standard Design Atlas (electrical data of ordinary buildings 04dz1kloc-0/)).
Pjs=4 14.75kW
Apparent power Sjs=Pjs/cosφ (see page 23 for power factor)
Sjs=4 14.75/0.9=460.84kVA
It is recommended to use 500kVA transformer.