Determine the main dimensions, number of turns and cross section of conductor of a 400 KVA, 11KV/440 V, 50Hz, 3 phase core type transformer with data, three step core, emf per turn= 8V ,maximum flux density= $1.2Wb/m^2$ , current density =$1.8 A/mm^2$, window space factor =0.2, stacking factor=0.9, height of window =3 times width of window.