Delta total line current - Basic electricity problem
This needs phasors because your motors take a little inductive currents and the lamps act as resistors. The motors are Y-loads but the lamps are a D-load, which cause harmful interline currents. Fortunately the lamp banks are identical, so the equivalent resistive Y-load exists. Find it and add the single line currents as phasors. Note that delta to Y transform is not a must, it only makes the number of needed phasors a little smaller.