An ideal gas expands isothermally from a volume V1 to V2 and then compressed to original volume V1 adiabatically. Initial pressure was P1 and final pressure was P3. The total work done is w, then:
a. P3>P1 , w=+ve
b. P3<P1 , w=−ve
c. P3>P1 , w=−ve
d. P3=P1 , w=0