Transformer wire size

[Shakirel]

I need some help in choosing the right wire size for a push-pull transformer that has 12v(min of 9 ,max of 18) input and 350v output.
The Ae=76mm^2,and it is working at a switching freq of 100kHz.From the design i understand that the output is working at 200kHz.
175W input->150W output:so there are about 19.44 amperes at the input(worst case)and 0.428 amperes at output.