3. Consider a lattice model with My, sites on the left, and MB sites on the right, and NA indistinguishable particles on the left and NB particles on the right of a moveable barrier. NA and NB are xed, but Mg, and M]; can vary as the barrier moves. 1 movable wall a) Find an expression for the entropy, S, of this system. Use Stirling's approximation (M and N large) to simplify. W b) Consider SMiMB) as the volume on the left changes M, sites MB with total M xed. Derive a relationship between Ma, Np, Particles N5 M3, Na and NB which must be satised at the maximum 3