Three 120/240 V panelboards are supplied with three subfeeders: A, B, and C. A is 50 ft, B is 100 ft, and C is 50 ft in length. The load on A is 15 kVA with a pf of 1.0; load B is 25 kVA with a pf of 0.95; and load C is 35 kVA with pf of 0.9. The three subfeeders are supplied with a 75 ft long main feeder. Determine the size of the main feeder and the three subfeeders. The allowance for voltage drop (line to neutral) is 1% for all conductors.

Assume THW copper conductors installed in a steel conduit. All the loads are noncontinuous and are protected by molded-case circuit breakers. The available symmetrical short-circuit current for all subfeeders and the main feeder was found to be 20,000 A.