Consider a simple series circuit consisting of an AC voltage source, resistor, inductor and a load (either purely resistive or purely capacitive). Select the component values such that in Case 1 (resistive load), the current lags the voltage (lagging power factor), and for Case 2 (capacitive...
Divide your load kva (400) by 8.6 and this defines the kva requirement of each single phase transformer. The 385A load current must flow through the 120VAC winding of the single phase transformer being used as the autotransformer. Thus, 385 x 120 = 46,200 VA for each transformer.