1. The problem statement, all variables and given/known data The question is presented as picture. 2. Relevant equations What is the expression of this 'heat capacity C'? The x-process is isothermal then C=nCΔT=0? Please give me some ideas. 3. The attempt at a solution set V1=V2, V3=V4, T1=T4, T2=T3, p1+p0=p2, p3-p0=p4 constant volume process:ΔU=n*Cv*(T2-T1)=Cv*V1*p0/R where p0=p2-p1 isothermal process:W=nRT1*ln(V3/V2)=nRT1*ln(p2/p3) Then I can't go any further.