**1. The problem statement, all variables and given/known data**

A certain fluid of mass 1kg undergoes a cycle of processes in a piston and cylinder device as follows:

Process A-B: 70kJ of work done on the fluid. 35kJ of heat rejected to surroundings

Process B-C: 50kJ of heat transferred to the fluid. No change in internal energy of system.

Process C-A: 100kJ of work done by the fluid, fluid returns to the initial state.

Calculate the heat transferred to or from the fluid in process C-A.

**2. Relevant equations**

I know that ΔU=Q-W is a relevant equation as I have been able to work out the other parts of this question that I have not written here with it, this part is actually the first part of the question but I am finding it the hardest to see what to do here :redface:

**3. The attempt at a solution**

I dont know whether you are supposed to use some of the values listed in Process A-B again or am I missing something?

http://ift.tt/1mY9loV