Eighteen, 250 KCMIL, THWN copper conductors are in a rigid metal conduit nipple. What is the minimum diameter in inches permitted by for the conduit? Assume that the conductors are not lead covered and the nipple is 1′ in length.

Eighteen, 250 KCMIL, THWN copper conductors are in a rigid metal conduit nipple. What is the minimum diameter in inches permitted by for the conduit? Assume that the conductors are not lead covered and the nipple is 1′ in length.