Internal energy and pv diagrams

[coffeem]

[PLAIN]http://img689.imageshack.us/img689/511/pistonquerstion.jpg

This is my part attempt...

[PLAIN]http://img830.imageshack.us/img830/7342/internalenergyanswer.jpg

And ideas on how I can do the rest of it?

 

[coffeem]

Actuall I think I have managed to work outish a). I used the first law of thermodynamics: E = Q + W

then giving that in the question it says: Q(isobarbic)= 200j

So since W = -PdV = -P(Vf-Vi)

I for internal energy of the syster at this point: U = 185j

Am I doing it right?