6. Sketch a PV diagram of the following processes. (a) A gas expands at constant pressure P1 from volume V1 to volume V2. It is then kept at constant volume while the pressure is reduced to P2. (b) A gas is reduced in pressure from P1 and P2 while its volume is held constant at V1. It is then expanded at constant pressure P2 to a final volume V2. (c) In which of the processes is more work done by the gas? Why?