1. The problem statement, all variables and given/known data I need to calculate dS/dU for a solid when then system is in thermal equilibrium. Na=100 Nb=10 U=20e 2. Relevant equations I rearranged the equation to find that Ds/Du=kb(1/omega)(dOMEGA/dU) 3. The attempt at a solution I am not sure how to go about this because I am not sure when the system is in thermal equilibrium and how to find (dS/dU) for the equation. any help would be greatly appreciated.