Halliday, Resnick & Walker — Temperature, Heat, and the First Law of Thermodynamics: Problem 75

Figure 18.31 displays a closed cycle for a gas. From \(c\) to \(b\), \(40 \text{ J}\) is transferred from the gas as heat. From \(b\) to \(a\), \(130 \text{ J}\) is transferred from the gas as heat, and the magnitude of the work done by the gas is \(80 \text{ J}\). From \(a\) to \(c\), \(400 \text{ J}\) is transferred to the gas as heat. What is the work done by the gas from \(a\) to \(c\)? (Hint: You need to supply the plus and minus signs for the given data.)