Consider an idealized model of a binary alloy as follows. An alloy is a crystal with N "sites, each of which can be occupied by an atom of type A or an atom of type B. No sites are empty. If a site is occupied by an atom of type A, then its energy is EA; if a site is occupied by an atom of type B , then its energy is 65. (a) What is the energy of the crystal if N A out of the N sites are occupied by atoms ' of type A and the rest of the sites are occupied by type B atoms? (b) .What is the entropy of the system described in part (a)? (c) If the alloy is in equilibrium at a temperature T, calculate the average value of N A. (Use Stirling's approximation in the form ln(N!) = N ln(N) N to simplify all factorials,)