I'm using the Modern Physics by Tipler (6th edition) book. In sec 7.1 it talks about the first excited state being either E_(112 ) E_(121 ) E_(112). My question is what is the process of finding the n_(1),n_(2),n_(3) quantum numbers ? How i understand you pick random values and from their find the order of energy levels. Can you give the process if would take of finding lets say the 4th excited state for both a cubic and non cubic box. Thank you for your time. PS: I apologize if my format is incorrect this is my fist post. The "_" represent subscript.