Chapter 5, Problem 18QP

Use the following diagrams for Problems 5.17 and 5.18.

The diagram on the far left shows a system before a process. Determine which of the diagrams on the right could represent the system after it undergoes a process in which (a) work is done on the system and $\Delta U$ is negative: (b) the system releases heat and $\Delta U$ is positive; (c) the system absorbs heat and $\Delta U$ is positive.