An ideal gas is expanded isothermally from 20 L to 30 L. During this process, 6 J of energy is expended by the external mechanism that expanded the gas. Which of the following statements is correct?
a. 6 J of energy flow from surroundings into the gas.
b. No energy flows into or from the gas since this process is isothermal.
c. None of the above statements is correct.
d. 6 J of energy flow from the gas into the surroundings.