Winnie- I follow your approach and that means you did an excellent job of explaining. Tough to do, I've taught code classes for a number of years and so I appreciate your detail. There is however a "Fly in the ointment" as they say. Based on Bob's problem our conductor sizing also needs to comply with NEC Article 424.3 Section 423.3(B). This IMHO would require us to upsize the conductors by 25%;
I came up with a 1/0 conductor and a voltage drop of 4.88v. and would be within the recommended 3% max.
