1. The problem statement, all variables and given/known data Consider the heating of a house by a furnace, which serves as a heat-source reservoir at a high temperature TF. The house acts as a heat sink at temperature T, and heat |Q| must be added to the house to maintain this temperature. Heat |Q| can of course be transferred directly from the furnace to the house, as is common practice. However, a third heat reservoir is readily available, namely, the surroundings at temperature T ., which can serve as another heat source, thus reducing the heat required from the furnace. Given that TF = 810 K, T = 295 K, Tσ = 265 K. and |Q| = 1,000 kJ, determine the minimum amount of heat |QF| which must be extracted from the heat-source reservoir (furnace) at TF . No other sources of energy are available. 2. Relevant equations 3. The attempt at a solution I am not sure if the way I am interpreting the question is right. There are some seemingly obvious mistakes, such as saying that the outside temperature helps reduce the amount of heat needed by the furnace.