(15) Consider a two-state Schottke model in which the excited state has energy 0 and the ground state has energy -. Sketch the energy vs temperature within the two approaches below. Your sketch should consist of two curves on one plot. Note that you do not need to do an actual derivation here if you do not want to - just show the sketch. a. The exact classical solution to this model. b. A perturbative approach wherein you use as a reference state a scenario in which both the excited and ground states have 0 energy, and you treat the energy of - in the ground state as a perturbation to this reference state.