1. The problem statement, all variables and given/known data Show that the total weight w of an assembly in thermal equilibrium is a maximum. 2. Relevant equations S= k ln W? dS = dQ/ T ? S is maximize when thermal equilibrium is reached. 3. The attempt at a solution First of all, i don't know what does "total weight w" means. Dose it means the number of ways W that a total of N particles can be classified into energy levels? I think that I have to establish a equation W = f(S) and use differentiation to prove that it is a maximum. However, i have no clue to start my work. Can someone give me some clues so that i can start my work? Thank you.