Grounded conductor size

[daiashi]

An office building service has a total computed load of 200 amps for each
ungrounded conductor and 60 amps for the grounded conductor.Equipment
terminations are 75 C , type THW copper.What is the minimal size for the
grounded conductor?

(A) 6 AWG
(B) 4 AWG
(C) 2/0 AWG
(D) 3/0 AWG

I get 4 AWG.

 

[walkerj]

That neutral needs to be able to support the whole of either phase

 

[bphgravity]

Assuming the neutral load has been figured by applying 250.61 and assuming the service entrance conductors are based on T310.16, I too would pick #4 in compliance with 250.24(C)(1) and T250.66 of the NEC.