An ideal monoatomic gas is taken round the cycle ABCDA as shown in ﬁgure. The work done during the cycle is:
Net work done during a complete cycle is equal to area under the cycle.
This is basically the work done in the constnant pressure processes, constant volume processes will not do any work.
The work done is 2P(2V-V) - P(2V-V) = PV.
'w' is work done on the gas which is negative of the pressure volume work, which gives us -PV as the answer.