An ideal gas is taken through the cycle A→B→C→A, as shown in Fig. If the net heat supplied to the gas in the cycle 15J, the work done by the gas in the process C→A is _____ J.

From given information  PC=70  Nm−2∴  work done  =  −12(70+100)×1=  − 85 JAlternative method :dQ= du+dw  in cyclic process du=0 dQ= dw     dw= work done in AB +Work done in BC+work done in CA  15= 100( 2-1) + 0 +Work done in CAWCA=-85 joule