Okay, I thought that I got these two easy problems but for some reason I'm making them hard. The first problem reads like this. "A heat engine operates between a tank containing 1*10^3 m^3 of water and a river at a constant temperature of 10 degrees Celcius. If the temperature of the tank is initially 100 degrees Celsius, what is the maximum amount of work that the heat engine can perform?" At first I thought that I would just find the efficiency of the engine by using the temperatures after converting them to degrees Kelvin and then use it to find the work. But that information about the volume is bothering me. Did the author put it for some reason in there? If so what would I use it for exactly and how? The second problem is pretty similar except there are two tanks and both of them have the same volume. If anyone knows how to deal with these problems and could respond I would be so grateful.