Please answer this and explain how you did it

Two large thermal reservoirs, one hot, temperature TH, and one cold, temperature TC are briefly put into thermal contact, so that a quantity of heat, Q, is transferred from the hot reservoir to the cold reservoir. (vii) Derive an expression for the entropy change in each reservoir. Justify any equations that you use for this irreversible process. [Mark: 12 percent] (viii) Discuss the net entropy change for the total system. [Mark: 4 percent]